(Kamafugitic/Leucititic) and –Free (Lamproitic) Ultrapotassic Rocks and Associated Shoshonites from Italy: Constraints on Petrogenesis and Geodynamics

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Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints on petrogenesis and geodynamics

Sandro Conticelli, Marinella A. Laurenzi, Guido Giordano, Massimo Mattei, Riccardo Avanzinelli, Leone Melluso, Simone Tommasini, Elena Boari, et al

Journal of the Virtual Explorer, Electronic Edition, ISSN 1441-8142, volume 36, paper 20 In: (Eds.) Marco Beltrando, Angelo Peccerillo, Massimo Mattei, Sandro Conticelli, and Carlo Doglioni, The Geology of Italy: tectonics and life along plate margins, 2010.

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Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints on petrogenesis and geodynamics

Sandro Conticelli 1. Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via Giorgio La Pira, 4, I-50121, Firenze, Italy. Email: [email protected] 2. Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Via Giorgio La Pira, 4, I-50121, Firenze, Italy.

Marinella A. Laurenzi Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Via Moruzzi, 1, I-56124, Pisa, Italy

Guido Giordano Dipartimento di Scienze Geologiche, Università degli Studi di Roma III, Largo San Leonardo Murialdo, 1, I-00146, Roma, Italy.

Massimo Mattei Dipartimento di Scienze Geologiche, Università degli Studi di Roma III, Largo San Leonardo Murialdo, 1, I-00146, Roma, Italy.

Riccardo Avanzinelli Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via Giorgio La Pira, 4, I-50121, Firenze, Italy.

Leone Melluso Dipartimento di Scienze della Terra, Università degli Studi di Napoli Federico II, Via Mezzocannone, 8, I-80138, Napoli, Italy

Simone Tommasini Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via Giorgio La Pira, 4, I-50121, Firenze, Italy

Elena Boari Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via Giorgio La Pira, 4, I-50121, Firenze, Italy

Francesca Cifelli Dipartimento di Scienze Geologiche, Università degli Studi di Roma III, Largo San Leonardo Murialdo, 1, I-00146, Roma, Italy.

Giulia Perini Scuola Secondaria di I° Grado Enrico Fermi, Via Enrico Fermi, 4, I-52020, Laterina (AR), Italy.

Abstract: In Italy and surroundings, leucite-free (i.e., lamproites), leucite-bearing (i.e., kamafugites, leucitites, plagioclase-leucitites), and haüyne-bearing (i.e., haüynites, haüyne-leucitites) ultrapotassic igneous rocks have been recorded from Oligocene to present in association with shoshonitic, and high-K calc-alkaline volcanic rocks.

The oldest outcrops of ultrapotassic and related rocks are found within the western Alps in the form of lamprophyric to calc-alkaline dykes intruded during the Oligocene. Four different magmatic provinces, characterised by the association of ultrapotassic igneous rocks with shoshonitic to calc-alkaline series, are also found along the Tyrrhenian margin of the peninsula. These rocks have been produced from Miocene to Holocene with an eastward/southeastward migration with time. Leucite-free silica-rich ultrapotassic lamproitic rocks are restricted to the early stages of magmatism, whereas ultrapotassic leucite-bearing rocks to the middle and late stages.

Mafic ultrapotassic igneous rocks are enriched in incompatible trace elements, with variable fractionation of Ta, Nb, and Ti with respect to Th and Large Ion Lithophile elements, and variable enrichment in radiogenic Sr and Pb and unradiogenic Nd. These characteristics are reconducted to sediment recycling within the upper mantle via subduction. Recycling of carbonate-rich pelites plays an important role in the genesis of leucite-bearing magmas. Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/

Large volume of metasomatic components is predicted to be accommodated within a vein network in the sub- continental lithospheric mantle. Partial melting of the vein generates ultrapotassic magmas, either lamproitic or kamafugitic. Increased interaction between the metasomatic veins and the surrounding mantle dilutes the alkaline component producing shoshonites and high-K calc-alkaline suites. The addition of a further subduction-related component shortly before magma generation is required to explain the isotopic composition of rocks from the Neapolitan district, together with the probable arrival of a within-plate component from the Adria mantle through slab- tear.

Citation: 2010. Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints on petrogenesis and geodynamics. In: (Eds.) Marco Beltrando, Angelo Peccerillo, Massimo Mattei, Sandro Conticelli, and Carlo Doglioni, Journal of the Virtual Explorer, volume 36, paper 20, doi: 10.3809/jvirtex.2010.00251 Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/

Dedication Figure 1. Distribution of ultrapotassic and related volcanic and sub-volcanic rocks in Italy and surroundings The present paper is dedicated to the memories of Fabrizio Innocenti and Renato Funiciello who passed away on January 27th, 2009 and August 14th, 2009, respectively.

Brief historical outline and lithologic terminology The potassic magmatism in the Central Mediterranean area developed through time from Oligocene to present, the last eruption of leucite-bearing magmas occurring in 1944 A.D. at Vesuvius. A pioneering comprehensive study performed by Washington (1906) grouped the several magmatic potassic and ultrapotassic suites in three different magmatic regions on the basis of sole mineralogical and petrographic characteristics: the Tuscan, Ro- man and Apulian regions. These regions were established without any temporal constraints. Washington (1906) did not describe and group the potassic volcanic rocks from Western Alps, Corsica, Tuscan Archipelago, and intra- Apennine area (Umbria). Washington (1906) also used a local lithologic terminology with rocks terms ranging The picture has been modified after Conticelli et al., from Vulsinite, Ciminite, Vicoite, Italite, Sommaite, etc.; 2007, 2009b; Avanzinelli et al., 2008, 2009. rock names not used anymore in the international termi- Avanzinelli et al. (2009) grouped the potassic and as- nology (Le Maitre et al., 2002). sociated volcanic rocks of the Central Mediterranean No further comprehensive studies have been per- area, by integrating the original division of Washington formed until the early sixties when Marinelli (1961, (1906) with the geochronological and genetic relation- 1967) reviewed the rocks of Tuscan Magmatic Region, ships, following the criteria suggested by Turner & Ver- including both mantle derived igneous rocks and crustal hoogen (1960). A division in four Magmatic Provinces anatectic ones, volcanic and intrusive, cropping out in the has been proposed. The Western Tyrrhenian (Corsican) same area from Pliocene to Pleistocene. This study has Magmatic Province is the westernmost one, with few somewhat complicated the general petrogenetic grid for magmatic products belonging to volcanic suites ranging potassic magmas. Some of the mafic Mg-rich rocks from from leucite-free ultrapotassic to high-K calc-alkaline of Tuscan region have been subsequently interpreted as the Miocene-Pliocene age (Fig. 1). During Pliocene – Pleis- result of complicate processes of enrichment in MgO, Ni, tocene, the volcanism migrated eastward to form the Tus- Cr and other compatible elements by gaseous transfert, can Magmatic Province (Fig. 1) with emplacement of starting from a granitic parental magma, of ultimate con- volcanic rocks belonging to leucite-free ultrapotassic to tinental crustal origin (Mazzuoli & Pratesi, 1963; Barberi shoshonitic and calc-alkaline magmatic suites (e.g., Pec- & Innocenti, 1967; Innocenti, 1967; Barberi et al., 1971). cerillo et al., 1988; Conticelli & Peccerillo, 1990, 1992; This brought also to perpetuate the hypothesis that leu- Conticelli et al., 1992, 2001, 2004, 2007, 2009a, 2011a,b; cite-free, Mg-rich, ultrapotassic magmas might have been Conticelli, 1998; Peccerillo, 1999, 2005a; Perini et al., generated by either direct partial melting of the continen- 2000, 2003). Coeval intrusive to volcanic silicic rocks of tal crust or by interaction between leucitic magmas and crustal derivation by anatexis have been kept separated crustal derived granitic melts (e.g., Taylor & Turi, 1976; because they do not have a common origin, although in Turi & Taylor, 1976; Vollmer, 1976, 1977, 1989; Vollm- some cases hybridization between mantle and crustal de- er & Hawkesworth, 1980; Vollmer et al., 1981; Turi et rived magmas have been recorded (e.g., Poli et al., 1984; al., 1991; Gasperini et al., 2002).

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Pinarelli et al., 1989; Pinarelli, 1991; Innocenti et al., Figure 2. Chemical classification of Ultrapotassic volcanic 1992; Poli, 1992, 2004). A further southeastward migra- rocks tion of volcanism during Pleistocene brought to the emplacement of the leucite-bearing ultrapotassic rocks of the Roman Magmatic Province, which in some cases are associated with younger shoshonitic to calc-alkaline suites (e.g., Conticelli et al., 1991, 2002, 2009b; Pecceril- lo, 2005a,b, and references therein; Boari & Conticelli, 2007; Frezzotti et al., 2007; Boari et al., 2009a). The volcanic activity of the Roman Magmatic Province pierced the boundary with the Holocene in its southernmost district, in the Neapolitan area, where a cluster of four volcanoes with historical volcanic activity occurs(i.e., Is- chia, Procida, Phlegrean Fields and Vesuvius volcanoes; Peccerillo, 2005a, and references therein). The Lucanian Magmatic Province is the easternmost volcanic area with the association of Pliocenine haüyne- to leucite-bearing Resemblance classification diagrams after Foley et al. ultrapotassic rocks (e.g., Peccerillo, 2005a and references (1987), which should be used only with ultrapotassic rocks. In the transitional field fall also some rocks be- therein; De Astis et al., 2006; Avanzinelli et al., 2008). A longing to the shoshonitic series but that matches carbonatitic lava has also been found in the activity of the with the requirements for being considered ultrapo- Monticchio volcano, during the final stage of the Lucani- tassic. an Magmatic Province (e.g. D’Orazio et al., 2007, 2008; The lamproite clan is made up by Mg-rich alkaline Stoppa et al., 2008). ultrapotassic volcanic to hypabyssal rocks (Foley & Ven- The volcanic suites turelli, 1989). According to Foley et al. (1987), the relatively low Al O , FeO , CaO and Na O counterbal- Ultrapotassic rocks have been defined using chemical 2 3 Tot 2 anced by extremely high MgO, and extremely variable parameters after Carmichael (1971) and Foley et al. silica contents, the latter ranging from basic to intermedi- (1987). A volcanic rock is considered ultrapotassic when ate compositions are distinctive characteristics (Table 1). it has K O > 3 wt. % concomitantly to K O/Na O = 2 2 2 2 Lamproites are invariably plagioclase-free ultrapotassic (Le Maitre, 2002). Mineralogical classification of potas- rocks, characterized by highly forsteritic olivine, chro- sic and ultrapotassic rocks is far from being exhaustive mian spinel, Al-poor clinopyroxene, K-richterite, sani- and produced a plethora of rock names due also to het- dine, picroilmenite, apatite (Fig. 3); leucite might be eromorphism (Yoder, 1986). Indeed lamproitic rocks on present in silica-undersaturated lamproites, but they have the basis of their mineralogy are made up by a large vari- never been observed among the lithologies found in the ety of different rock types; fitzoyite, cedricite, orendite, Central Mediterranean (i.e., Corsica, and Tuscany). madupite, wolgidite, cancalite, jumillite, verite, and for- The lamprophyre (calc-alkaline) clan is an category tunite are some of the most common lamproitic terms. To of sub-volcanic rocks found at convergent plate margins avoid this problem and to provide unequivocal classifica- (Rock, 1989). Their names are based on the mineralogy, tion, Foley et al. (1987) suggested a chemical division in on the basis of the occurring feldspar and of the possible three different clans on the basis of chemical parameters: occurrence of amphibole (Le Maitre, 2002); minette, the lamproite, kamafugite, and Roman (plagioclase-leuci- spessartite, and kersantite are the rock names. They are titic; Foley, 1992a) clans (Fig. 2). In Italy ultrapotassic potassic to ultrapotassic with higher alumina and lime rocks are associated in time and space also with calc-al- with respect to lamproites (Table 1), but in some cases kaline lamprophyres, shoshonitic and high-K calc-alka- they are chemically very similar to lamproitic and transi- line volcanic rocks, and at Monticchio volcanic field, tional ultrapotassic rocks (Fig. 2) on the basis of the crite- within the Lucanian Magmatic Province, with alvikites. ria suggested by Foley et al. (1987).

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The kamafugite clan is a group of rare kalsilite-bear- larnite normative. According to the definition of Foley et ing melilitites described for the first time by Holmes & al. (1987), kamafugite clan is made up by Mg-rich alka- Harwood (1932) and Holmes (1940). Because of the ex- line ultrapotassic volcanic rocks characterised by rela- treme mineralogical variability each rock recorded has tively low SiO2, Al2O3 and FeOTot but extremely high taken the name of the locality where it was discovered, CaO and Na2O contents (Fig. 2; Table 1). Kamafugites but heteromorphism do also occur as in lamproites (Yod- are feldspar-free rocks although dominated by kalsilite, er, 1986); Sahama (1974) suggested to keep the old nepheline, and sometimes leucite as felsic phases and oli- names (i.e., katungite, mafurite, ugandite) for each single vine, clinopyroxene, phlogopite, and melilite (Fig. 3) rock, but to collect them in a unique clan with a root among the mafic ones (Sahama, 1952, 1954, 1960; Grag- name from the acronym of the African members: nani, 1972; Yoder 1976, 1979; Gallo et al., 1984; Cun- Katungite – Mafurite – Ugandite. Gallo et al. (1984) dari & Ferguson, 1991; Conticelli & Peccerillo, 1992). suggested the inclusion in the kamafugite clan also of the The Roman rocks are leucite-bearing silica undersa- Italian terms, such as the coppaellite and the venanzite. turated ultrapotassic rocks and they are known worldwide Kamafugitic rocks are ultrapotassic but strongly silica since the original work by Washington (1906). Original- and alumina undersaturated; with this respect they are ly, a plethora of names has been used also for this group

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 6 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ of rocks. These names recall the occurrence locality for Stoppa & Woolley (1997) made a review of the possible the specific rock type (e.g., vulsinite, ciminite, cecilite, occurrence of carbonatite-like rocks in Italy, but some of vicoite, italite, etc.). Le Maitre (2002) suggested a classi- them have been questioned to be real carbonatites. In fication based on mineralogical and chemical parameters some cases they have been classified as pyrometamor- (Total Alkali Silica), thus leucite-bearing basanite, teph- phic rocks due to either natural or anthropogenic rite, phonolitic tephrite, tephritic phonolite, and phonolite combustion of marly sedimentary rocks (e.g. Melluso et are presently the basic names beside the term leucitite. al., 2003, 2005a, 2005b; Capitanio et al. 2004; Stoppa et All these rocks might be classified in a group name al., 2005), in other cases some of them have been ques- termed leucitite and plagio(clase)-leucitite clan on the tioned as the result of carbonate sintexis to provide a base of the frequent occurrence of modal plagioclase (Fo- wide spectrum of minerals, according to the findings of ley, 1990a). According to the definition of Foley et al. Tilley (1952), resulting in a dilution of major and trace (1987) the leucitite and plagio(clase)-leucitite clan (i.e., element contents, but not of CaO (Peccerillo 1998; Pec- Roman rocks) is made up by alkaline ultrapotassic vol- cerillo, 2004, 2005b, Wolley et al., 2005). Unquestioned canic rocks characterised by widely variable MgO, with mantle-derived alvikitic rocks have been documented at relatively low SiO2, and FeOTot, but relatively high CaO, Monticchio monogenetic field (e.g., Jones et al., 2000; Al2O3, and Na2O contents (Fig. 2; Table 1). This group D’Orazio et al., 2007). of rocks was also defined by Appleton (1972) as high po- The shoshonitic series is a magmatic sequence of tassium series. The relative acronym, HKS, has been rocks mildly enriched in potassium, with variably silica widely used in the specific scientific literature about Ro- saturated terms in the most evolved rocks. The rock types man rocks. We prefer the use of the leucitite and plagio- range from potassic trachybasalt (shoshonitic basalt) to leucitite clan because self explanatory of the main min- trachyte, passing through shoshonite s.s. and latite. These eralogical characteristics of these rocks, and not locally rocks have variable enrichment in K2O in the most primi- related to the Italian magmatism. Leucite is ubiquitously tive terms. No definitive boundary between ultrapotassic present with plagioclase missing only in the most silica clans and shoshonitic series has been drawn on the K2O undersaturated terms (Fig. 3). vs. silica diagram (Peccerillo & Taylor, 1976); in some The haüyne-bearing clan is made up by highly silica cases shoshonites are ultrapotassic rocks as well (e.g., undersaturated volcanic rocks characterised by high lev- Conticelli et al., 2011b,c) and they fall within the field of els of both K2O and Na2O (De Fino et al., 1987; Becca- transitional group IV ultrapotassic rocks (Fig. 2) accord- luva et al., 2002). Haüyne is also found as phenocryst ing to the classification scheme of Foley et al. (1987). In along with leucite and rarely nepheline (Table 1; Fig. 3). Italy this group of rocks has been originally recognised These rocks are confined in the Lucanian Magmatic by Appleton (1972) at Roccamonfina volcano, who dis- Province and have low silica contents. They are found as- tinguished them as a low potassium series (LKS) group sociated to melilite-bearing rocks and alvikites. from the leucite-bearing ultrapotassic series (high potas- All rocks with approximately 50 % vol. of carbonate sium series; HKS). Later Civetta et al. (1981) renamed minerals can be classified as carbonatite. Calcium-, them as potassic series (KS) keeping the Appleton’s Magnesium- and Iron carbonatite are divided on the basis (1972) name for the leucite-bearing terms. Conticelli & of the main carbonate phase in the mode of the rock; Peccerillo (1992) interpreted the rocks belonging to this namely calcite, dolomite, ankerite. Alvikites is a silica- series as transitional (TRANS) from ultrapotassic series rich calcium-carbonatite that is distinguished by Sövite to calc-alkaline series. Conticelli et al. (2004) preferred on the basis of trace element contents (Le Bas, 1999). A the use of shoshonite the official names provided by hot debate about the occurrence of primary carbonatite IUGS (Le Maitre, 2002). clan in Italy is open since the end of the last century.

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Figure 3. Microphotographs of thin sections of ultrapotassic and related volcanic and sub-volcanic rocks in Italy and surroundings

Photos have been performed at polarized microscope by Sandro Conticelli and Leone Melluso. White bar is 2 mm long. Legend: apa = apatite; bio = biotite; cpx = clinopyroxene; haü = haüyne; leu = leucite; mel = melilite; ne = nepheline; olv = olivine; phl = phlogopite; plg = plagioclase; sd = sanidine. Localities and Magmatic Provinces: A) Orciatico, Tuscan Magmatic Province; B) Torre Alfina, Tuscan Magmatic Province; C) Torre Alfina, Tuscan Magmatic Province; D) Radicofa- ni, Tuscan Magmatic Province; E) Monte Amiata, hybrid volcano; F) Vesuvius, 1631-1944 A.D., Roman Magmatic Prov- ince – Neapolitan District (ND); G) Roccamonfina, Roman Magmatic Province; H) Vulsini, Roman Magmatic Province; I) San Venanzo, Roman Magmatic Province; J) Cupaello, Roman Magmatic Province; K) Pedra della Scimmia - Vulture, Lu- canian Magmatic Province; L) Melfi - Vulture, Lucanian Magmatic Province.

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The high-K calc-alkaline and calc-alkaline series northern Apennines during the Late Cretaceous in the are defined on the basis of K2O contents with respect to Ligurian oceanic domain, which was deformed during silica (Peccerillo & Taylor, 1976). They also match the Late Cretaceous to Early Eocene time, and formed a dou- chemical and mineralogical parameters provided by Ar- ble vergent accretionary wedge, now outcropping from culus (2003). They are sub-alkaline rock with terms rang- Corsica to the Italian peninsula (Treves, 1984; Carmigna- ing from basalts to rhyolites, passing through basaltic an- ni et al., 1994). Starting from the Oligocene onwards, desite, andesite, and dacite (Le Maitre, 2002). The pre-fix foredeep basins migrated eastward and formed on the top high-K is added when needed according to the Peccerillo of continental crust, pertaining to the passive margin of & Taylor’s (1976) scheme (Fig. 8b). These rocks are Apulia. Their incorporation into the Apenninic orogenic more represented within the ultrapotassic association of wedge marked the subduction of Adriatic continental the Italian pensula than previously though (Di Girolamo lithosphere underneath Europe. Afterwards, during the et al., 1976; Perini et al., 2000; Conticelli et al., 2004, Neogene, the foredeep basins further migrated toward the 2009a, 2010a,b; Boari & Conticelli, 2007; Frezzotti et Apulia foreland ahead of the eastward migrating orogenic al., 2007; Boari et al., 2009a). front. Foredeep basins formed on top of progressively more external units, with an eastward migration and dur- The Geodynamic framework ing the Quaternary reached the configuration in the Adri- The present-day structure of the Central Mediterra- atic foreland, where the foredeep deposition ceased (Ci- nean region derives from the convergence of Africa and pollari & Cosentino, 1995, and references therein). Dur- Eurasia, which over the Tertiary occurred at about 1-2 ing the Quaternary the southeastward rollback of the sub- cm/yr on average, with a total value estimated in about ducting Ionian plate was expressed in the southern Apen- 400-500 km (Dewey et al., 1989). During such time, the nines by the progressive southeastward shifting (parallel Ionian-Adriatic lithosphere continuously subducted to- to the longitudinal axis of the chain) of the Bradanic fore- ward west and northwest underneath the Eurasia plate. deep basin (Tropeano et al., 2002, and references therein) This process led to the progressive closure of the inter- and of the Apenninic outer thrust front, which is present- vening Mesozoic oceanic basins of the Tethyan domain, ly located off-shore, in the Ionian Sea (Doglioni et al., with the formation of a complex arcuate orogenic belt 1999 and references therein). (Apennine- Maghrebide belt) and extensional back-arc In the central-western Mediterranean, differential basins (Ligure-Provençal and Tyrrhenian basin) (Dewey trench retreat of the Ionian-Adriatic slab caused the for- et al., 1989; Horvath & Berckheimer, 1982). The sub- mation of the Liguro-Provençal and Tyrrhenian back arc ducting slab is still recognizible beneath the Calabrian basins (Malinverno & Ryan, 1986; Lonergan & White, arc, where deep seismicity is detected along a narrow (~ 1997; Faccenna et al., 2001; 2004). The Liguro-Proven- 200 km) and steep (70°) Benioff plane dipping north- çal spreading took place simultaneously with the east- westward down to about 500 km. Continental collision is ward drift of the Corsica-Sardinia block, which rotated probably still active in the central-northern Apennines, counterclockwise about a pole located north of Corsica where intermediate earthquakes occur down to 90 km (e.g., Van der Voo, 1993; Speranza et al., 2002 and refer- (Selvaggi & Amato, 1992; Carminati et al., 2005). ences therein). Rifting and drifting processes in the Cor- The Africa-Eurasia convergence and the consequent sica-Sardinia were related to the southeastward retreat of subduction of the Ionian-Adriatic lithosphere, resulted in the subducting Ionian slab, and were accompanied by the building of the Alps-Apennine belts. The main geo- arc-related volcanism, which appeared first in Sardinia logical evidence of such process within the Apennine (~32My) and in Provençe and continued until ~14 My in chain are the deposition of thick siliciclastic deposits in southwestern Sardinia (i.e., Beccaluva et al., 1985; Lus- the foredeep basins and the HP/LT metamorphism, in the trino et al., 2004). internal part of the orogenic wedge (Jolivet et al., 1998). After the end of the Corsica-Sardinia drifting, back- In the Apennines, the migration of the orogenic front is arc extension continued in the southern Tyrrhenian Sea. marked by the onset of siliciclastic deposits, which are In this basin, oceanic crust formed diachronously in two progressively younger toward the Adriatic-Ionian fore- sub-basins: between ~4.3 and 2.6 Ma the Vavilov basin land. The onset of siliciclastic deposition occurred in was formed, whereas the Marsili basin developed after

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~2 Ma (Marani & Trua, 2002; Nicolosi et al., 2006). kinematically independent microplates between Eurasia Seismic, structural and stratigraphic data on the on-shore and Africa. In particular, the distribution of earthquakes western Calabria-Peloritani terrane (Mascle et al., 1988; (Anderson & Jackson, 1987) and recent geodetic data Sartori, 1990; Mattei et al., 2002) suggest that rifting (Ward, 1994; D'Agostino and Selvaggi, 2004; Goes et started along the western margin of the southern Tyrrhe- al., 2004) shows that the Adriatic region currently moves nian Sea (Sardinian margin) during Serravallian, and pro- to NE respect to Eurasia, and has therefore an independ- gressively migrated south-eastward in the Vavilov (late ent motion relative to both the Nubia and European plates Messinian-Early Pliocene) and Marsili (Late Pliocene- (Fig. 4). Early Pleistocene) basin. In the northern Tyrrhenian Sea Figure 4. GPS velocities relative to Eurasia of continuous lithospheric extension caused the formation of Neogene stations in Italy. sedimentary basins. N-S to NW-SE oriented extensional basins developed on the previously thickened Alpine crust in the hinterland, contemporary with flexural basins in the foreland (e.g., Kastens et al., 1988) which get younger eastward as well documented by the age of the infilling sedimentary sequences. In the westernmost Tyr- rhenian sea these sedimentary sequences are Lower Mio- cene in age and are characterized by N-S trending east- dipping normal faults (Bartole, 1995) while they are Pleistocene in age in the Umbrian region, where extensional tectonics is presently active and most of the normal faults strike NW-SE and dip westward (Jolivet et al., 1998; Collettini et al., 2006).

Present day tectonics and kinematics Space geodesy investigations, the distribution of seismicity, geological, structural and paleomagnetic data provide a framework of the recent tectonic evolution of the Italian geodynamics, which is substantially different from that active during the Neogene and Pleistocene (until about 1 Ma), where the processes of subduction and opening of backarc basins do not appear active anymore (D'Agostino & Selvaggi, 2004; Goes et al., 2004; Mattei et al., 2007). The GPS data show that in Italy the current convergence between Eurasia and Nubia (the African Velocities relative to Eurasia defined from continuous plate with the exception of the region east of the East Af- stations in Italy of Global Positioning Systems. Error rican Rift) is about 5-6 mm / year and oriented NW (Fig. ellipse represents the 95% confidence interval (drawn 4) (Sella et al., 2002; D'Agostino & Selvaggi, 2004). The after D’Agostino & Selvaggi, 2004 and Mattei et al., 2008). study of earthquakes and tectonics, however, has recently suggested that the manner in which this convergence is These results are consistent with several geological absorbed along the margin between the two plates is ex- and paleomagnetic data that show a gradual deactivation tremely complex, given the coexistence of compressive of the compressional outer fronts of the Apennines and and extensional deformation along a wide area stretching Sicily, the gradual decrease of the subduction processes from north Africa to Greece, and affecting also the entire in the Italian region and the end of the curvature process- Italian peninsula (McKenzie, 1972; Pondrelli et al., 1995; es of the Northern Apennines and the Calabrian Arc Goes et al., 2004). The existence of areas with low or no (Mattei et al., 2004; Cifelli et al., 2007; Mattei et al., seismicity has suggested the possible presence of 2007). These data suggest that the convergence between

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Africa and Eurasia is currently absorbed by the motion of Southern Tyrrhenian margin, south of the Roccamonfina the Adriatic microplate, rather than by subduction of area, extensional tectonics started more recently than in Adriatic-Ionian lithosphere. At the same time geodetic the northern and central Tyrrhenian margin, with similar data show that the Adriatic area is kinematically inde- eastward temporal migration. In this region the onset of pendent from the Apennine area, which shows velocity the extension is marked by Late Pliocene syn-rift sedi- vectors oriented NNW respect to Eurasia, confirming the mentary marine deposits that crop out along the Tyrrhe- existence of a band of active deformation in the axis of nian coast of the Campania region. Extension later pro- the chain already highlighted by the study of seismicity gressed toward the axis of the Apennine chain, where and geological analysis (Valensise & Pantosti, 2001 and sedimentary basins are filled by lower-middle Pleisto- references cited). In this same area studies of deformation cene continental sequences (Cinque et al., 1993), and the based on geodetic triangulation shows that the region is largest (M > 6.7) historical and instrumental seismicity currently subject to an extension rate of about 3-5 mm/ ever recorded occurred. year NE-SW oriented (Hunstad et al., 2003), which is In Northern Apennines extensional tectonics is mostly consistent with the focal mechanisms and the distribution controlled by NW-SE oriented, east-dipping low-angle of the major historical and instrumental earthquakes normal faults and associated high-angle east-dipping nor- which occurred in the axial zone of the Apennine chain. mal faults. Low-angle normal faults gently dipping to- D’Agostino et al. (2008), on the base of GPS observa- ward the east, show evidence of present-day activity tions and earthquake slip vectors, suggest that the kine- along the axial part of the Apennine chain, whereas their matics of the Adriatic region is controlled by the pres- old equivalents are now outcropping along the western ence of two distinct microplates: Adria (corresponding part of the margin. Here exhumed normal faults have with the northern Adriatic region) and Apulia (corre- been widely recognized in the Alpine metamorphic units sponding with the southern Adriatic, Ionian and Hyblean in the Elba and Giglio Island, offshore Tuscany (Jolivet regions), whose relative motion controls the active defor- et al., 1998; Collettini et al., 2006). Toward the south, the mation in the central Adriatic Sea. The opposite rotations existence of low-angle normal faults is less evident and (counterclockwise for Adria and clockwise for Apulia) of active extension is mainly given by high-angle normal these two microplates respect to Europe are able to ex- faults, NW-SE oriented. In Central Apennines high-angle plain the present-day deformation pattern in the central active normal faults are mostly dipping toward the west. Adriatic region and represent the way in which the rela- Such faults show a long term tectonic activity, which is tive motion between Nubia and Eurasia is presently ac- responsible for the formation of large intermontane ex- commodated in the Central Mediterranean region. tensional basins, infilled by Late Pliocene-Quaternary continental sedimentary sequences (D’Agostino et al., Structural and geological features of the 2001; Cavinato et al., 2002). High-angle NW-SE orien- extensional Tyrrhenian margin ted, west dipping, normal faults are especially evident In the westernmost northern Tyrrhenian Sea, where along the axis of the Apennine chain. Conversely, toward the Western Tyrrhenian (Corsican) Magmatic Province the west normal faults are covered by Quaternary volcan- occur (Fig. 1), the sedimentary sequences that infill the ic deposits and their existence has been recognized by extensional sedimentary basins are Lower Miocene in means of geophysical investigations and deep boreholes age and they are bounded by N-S trending east-dipping drilled for geothermal research (Barberi et al., 1994). normal faults (Bartole, 1995), whilst in the Apennine re- In Southern Apennine, active normal faults are at gion they are Pleistocene in age, where extensional tec- high-angle and NW-SE oriented and they are either dip- tonics is presently active and most of the normal faults ping toward the east or toward the west. In particular, strike NW-SE. field observations and seismological data show that the In the central Tyrrhenian margin, the onset of exten- fault responsible of the Irpinia 1981 M = 6.5 earthquake sional tectonics can be dated at the Late Miocene because occurred along a NW-SE oriented east-dipping normal syn-rift sedimentary sequences have been recognized in fault (Westaway & Jackson, 1984; Pantosti et al., 1993), extensional basins located between the Tolfa-Cerite- Manziana and Roccamonfina volcanoes (Fig. 1). In the

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 11 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ whereas, some of the most important intermontane Qua- Thermal flow is generally characterized by very high ternary extensional basins are bounded by NW-SE west values all along the Tyrrhenian border of the central- dipping oriented normal faults. northern peninsula, from Tuscany to Campania, but dis- All along the extensional Tyrrhenian margin an im- continuously distributed. Southern Tuscany and northern portant role is exerted by transverse tectonic structures, Latium have high heat flow (>100 mW/m2), with local- NE-SW oriented, which either bound some of the major ised peaks (>600 mW/m2), which produce several geo- extensional sedimentary basins in the area, or represent thermal fields, with the Larderello one being the most fa- the tectonic elements along which the main segments of mous worldwide (Mongelli et al., 1991) (Fig. 5). Toward the NW-SE oriented normal faults reverse their dip direc- the south-east, thermal flow values are drastically re- tions (Faccenna et al. 1994a; Acocella & Funiciello duced within the Middle Latin Valley, the area comprised 2006; Barchi et al., 2007). In some cases NE-SW orien- between the Colli Albani and the Roccamonfina volca- ted faults also bound major NE-SW oriented extensional noes, as a consequence of the presence of thick carbonat- sedimentary basins (i.e., Baccinello-Cana, Cerite, Ardea, ic sedimentary sequences hosting huge karstic reservoirs, Garigliano), which formed parallel to the main, NE-SW which buffer heat flow to values lower than standard (30 oriented, stretching direction and play a major role to mW/m2). It is also noteworthy that the presence of con- transfer extension to the different segments of the NW- vective support to topography and strong attenuation of SE oriented normal faults. The NE-SW normal faults sys- seismic waves consistently suggest that a positive ther- tem is particularly important along the western side of the mal structure of the crust-mantle boundary is characteris- extensional Tyrrhenian margin, whereas assume a minor tic of a large region including the Apennine chain and its importance within the axis of the Apennine chain, where Tyrrhenian border from southern Tuscany to the Vulture extensional basins are NW-SE oriented. In particular, area (Mele et al., 1997; D’Agostino & McKenzie, 1999). NE-SW tectonic lineaments represent a major factor to control the location of Quaternary volcanoes all along the Figure 5. Heat flow and seismicity in Central Italy. western Italian peninsula. Most of the Quaternary volcanoes formed where NW-SE normal faults intersect transverse tectonic lineaments, which represent a preferential structure for magma upwelling and fluids emissions (Fu- niciello & Parotto 1978; Acocella & Funiciello 2006). Extensional tectonics along the Tyrrhenian margin of the Italian peninsula has produced significant crustal thinning, high thermal flow, mantle fluids, and a characteristic distribution of seismic activity along the Italian Tyrrhenian margin. Crustal thickness has been recently defined in detail along a transect from Northern Corsica to the Adriatic Sea in the framework of the CROP 03 project (Pialli et al. 1998; Collettini et al. 2006) and using receiver functions from teleseismic data (Piana Agos- tinetti et al., 2002; Di Bona et al., 2008). Results con- Heat flow and seismicity in Central Italy. Heat flow val- verge to show the upwelling of Moho in the Tyrrhenian ues are generally very high along the Central-Northern Tyrrhenian margin of the Italian peninsula (Mongelli & area, where Moho depth is about 22 km, and a progres- Zito, 1991). High values of heat flow correspond to a sive westward thickening of the continental crust as far as decrease in seismic activity, which is concentrated the Apennine chain, with a maximum crustal thickness of along very small areas corresponding to recent or active volcanoes or geothermal fields. about 35-38 km observed toward the Adriatic foreland. To the west, data indicate a partial overlapping between The extensional Tyrrhenian margin of the Apennine the deep Adriatic Moho and the shallower Tuscan Moho, chain is also affected by extensive CO2 degassing, mostly with a mantle slice embedded between two crustal slices. derived from a mantle source and representing a significant amount of the estimated global CO2 emitted from

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 12 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ sub aerial volcanoes (Collettini & Barchi, 2002; Chiodini century (Alvarez et al., 1996; Karner & Renne, 1998). et al., 2004; Miller et al., 2004). The anomalous flux of Quite often published age data related to the same vol- CO2 decreases toward the axis of the Apennine chain. canic units disagree. This is particularly true for several Here fluid overpressures, documented at depth by deep old K/Ar data, and there are many reasons to explain the boreholes, suggest that CO2-rich fluids can be trapped by observed discrepancies. K/Ar ages are in fact model ages, stratigraphic or structural seals and released to shallow because an atmospheric initial isotopic ratio is assumed reservoirs at hydrostatic fluid pressure, triggering the in their calculation, and if this is not the case the obtained main seismic events in the Apenninic chain (Miller et al., “age” value is older than the true one. Other “wrong” 2004). Strong historical and instrumental earthquakes ages likely derive from the use of altered mineral phases, have occurred along the axis of the Apennine chain, and as revealed by their non-stoichiometric K contents. A fur- represent the most important effect of active deformation ther possibility of biased younger K/Ar ages is limited to in the Italian peninsula. In this region the extensional ac- sanidines, which have difficulties to melt completely tive stress field is NE-SW oriented, with extension rate of (McDowell, 1983), with consequent underestimate of 2.5-3.0 mm/yr. Here, M>6.5 earthquakes nucleate in the 40Ar concentration. It is clear from the above considera- upper crust at depth between 5 and 12 km with exten- tion that 40Ar-39Ar data, when available, will be preferred sional focal mechanisms, in agreement with geodetic data to K/Ar data. (Hunstad et al., 2003) and borehole breakouts results Sometimes only age data obtained several years ago (Montone et al., 2004). Toward the Tyrrhenian margin with the K/Ar method are available for the geochronolog- seismicity decreases dramatically in correspondence with ical reconstruction. And rarely the whole set of products the abrupt increase of positive heat flow anomalies. In of a volcanic district has been dated and/or ages were in- this region seismic activity generally nucleates at very ferred from stratigraphic reconstructions. The geochrono- shallow level and is mostly concentrated along the active logical discussions on the various volcanoes and volcanic volcanoes and geothermal fields of the area (Fig 5). districts have different levels of deepening. Those areas having wide and recent geochronological data have on Geochronology and time of magmatism average short descriptions, whereas areas having few The first geochronological data related to the potassic and/or old data have often much longer discussions, and magmatism in the Central Mediterranean area date back sometimes new age calculations. There are many critical to many decades ago (Evernden & Curtis, 1965). Several points and open questions on the majority of volcanic data were accumulated with time, with variable geologi- districts, and several data are needed to constrain these cal confidence, with different accuracy and with an un- volcanic activities. Within the limits of published data, an even distribution on the various volcanic centers (e.g., effort was done at least to confine the beginning and the Marra et al., 2004 and Laurenzi, 2005 and references end of the known volcanic activity in each area. Pyro- therein). K/Ar and 40Ar-39Ar data constitute almost the clastic products are widespread and likely overwhelming bulk of the age data on the Italian ultrapotassic and asso- by volume among products of the potassic volcanism. ciated magmatic rocks, being data obtained with all other These products are often found as distal tephra within methods, as Rb/Sr, U-Th disequilibrium, Fission Tracks marine and continental sedimentary succession. Their use subordinated. 14C dating is quite widespread on products and their ages are beyond the scopus of this paper, due younger than 50 kyr, obviously limited to organic materi- also to the difficulty to identify precisely their prove- al found in and within volcanic products. nance. Hence only pyroclastic deposits of consistent During this long period of time the technological pro- width and clearly assigned to a volcanic district will be gress led to instrumental improvements which enabled considered. Within the limits of published data, we’ll try precise analyses on very small samples, at least for con- at least to confine the beginning and the end of the ventional K/Ar method and, above all, for 40Ar-39Ar known volcanic activity in each area. Mentioned age data method. It is sufficient to compare the weights of mineral published before 1977 have been recalculated with Steig- 40 39 separates used for the Ar analyses listed in Table 7 of Ev- er & Jäger (1977) constants. Ar- Ar ages, which are ernden & Curtis (1965) with the single crystal laser total relative to monitor ages that might not be strictly compa- fusion age data appeared in literature at the end of last rable, have not been normalised to a unique monitor and

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 13 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ monitor age. Consequent incidental age biases are well Monte Vulture volcano and the nested Monticchio lakes below the degree of detail of the following discussion, monogenetic field. which aims to give a chronological framework for the ultrapotassic volcanism. For the same reason, on average Figure 6. Age distribution of ultrapotassic and related volcanic and sub-volcanic rocks in Italy and surroundings. age errors are not shown. In the following paragraphs we will report a descrip- tion of the different magmatic provinces occurring in Ita- ly. This scheme follows the geographic location of Mag- matic Provinces and then of Volcanic Districts from Northwest to Southeast, which broadly correspond to the onset of ultrapotassic magmatism (Fig. 6 - data used for drawing figure are from the following selected list: Ever- nden & Curtiss, 1965; Krummenacher & Evernden, 1965; Barberi et al., 1967; Borsi et al.,1967; Carraro & Ferrara, 1968; Nicoletti, 1969; Hunziker, 1974; Lombardi et al., 1974; Basilone & Civetta, 1975; Civetta et al., 1978; Bigazzi et al., 1981; Radicati et al., 1981; Cassi- gnol & Gillot, 1982; Gillot et al., 1982; Metzeltin & Vez- zoli, 1983; Pasquarè et al., 1983; Sollevanti, 1983; For- naseri, 1985a, b; Laurenzi & Villa, 1985, 1987; Poli et al., 1987; Metrich et al., 1988; Savelli, 1983, 1988; Balli- ni et al., 1989a; Villa et al., 1989; D’Orazio et al., 1991; Turbeville, 1992; Cioni et al., 1993; Barberi et al., 1994; Laurenzi et al., 1994; Nappi et al., 1995; Laurenzi & De- ino, 1996; Bellucci et al., 1999; Pappalardo et al., 1999; Villa et al., 1999; Brocchini et al., 2000, 2001; Giannetti & De Casa, 2000; Conticelli et al., 2001; De Vivo et al., 2001; Giannetti, 2001; Karner et al., 2001a, b, c; Mascle et al., 2001; Altaner et al., 2003; Marra et al., 2003, 2009; Rolandi et al., 2003; Deino et al., 2004; Cadoux et al., 2005; Freda et al., 2006; Florindo et al., 2007; Rou- chon et al., 2008; Scaillet et al., 2008; Boari et al., 2009b; Cadoux & Pinti, 2009; Gasparon et al., 2009; Giaccio et al., 2009; Sottili et al., 2010). They are: i) the Oligocene Magmatism in the Western Alps; ii) the Mio- cene Magmatic events of the Western Tyrrhenian Mag- matic Province (Corsican); iii) the Plio-Pleistocene Mag- matic events of the Tuscan Magmatic Province; iv) the Monte Amiata, a Middle Pleistocene “hybrid” volcano; Age distribution of ultrapotassic and related volcanic v) the Pleistocene Magmatic events I: the Roman Mag- and sub-volcanic rocks in Italy and surroundings. For data source of geochronological data see text. matic Province including the Latian districts (e.g., Vulsi- ni, Vico, Sabatini, Colli Albani, Middle Latin Valley, and In each of these sections the ages reported are from a Roccamonfina), the intramontane Umbrian district thoughtful evaluation of the original geochronologic data. (found within the Apennine chain), and the Neapolitan district (i.e., Ischia, Procida, Campi Flegrei, and Somma- Oligocene Magmatism in the Western Alps Vesuvius volcanoes); vi) the Pleistocene Magmatic Syn to post-collisional magmatism related to the events II: the Lucanian Magmatic Province including the building of the Alpine chain is recorded in the southern

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 14 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ portion of the Alps, with emplacement and formation of and volcanoclastics sediments have been also found. hypabissal dykes, small plutons and volcano-sedimentary Legend: 1) low grade Permian granites and granodior- ites; 2) Ivrea zone mafic complex; 3) Ivrea zone knzi- rocks. They are widespread and petrologically diverse gitic rocks; 4) Internal Sesia-Lanzo zone (eclogitic mi- with a clear compositional geographical polarity, with caschists); 5) external Sesia-Lanzo zone (gneiss com- tholeiitic to calc-alkaline igneous rocks in Southeastern plex); 6) Schistés Lustrés and ophiolitic complex; 7) Monte Rosa and Gran Paradiso Nappe (orthogneiss- Alps, high-K calc-alkaline to calc-alkaline in Central es); 8) Oligocenic plutonic bodies (T = Traversella; Bi = Alps, and ultrapotassic, shoshonitic to high-K calc-alka- Biella); 9) Oligocenic volcanoclastic cover series; 10) line in Western Alps (e.g., Beccaluva et al., 1983). Post- Pleistocene-Holocene coves. Open squares represent sample localies of the work of Conticelli et al. (2009a). collisional ultrapotassic and related shoshonitic to high-K Modified after Dal Piaz et al. (1979); Venturelli et al. calc-alkaline igneous rocks are found within a restricted (1984); Callegari et al. (2004); Owen (2008); Conticelli area in the internal zone of the North-Western Alps (e.g., et al. (2009a). Dal Piaz et al., 1979; Callegari et al., 2004; Peccerillo & The age of the ultrapotassic and related magmatism in Martinotti, 2006; Owen, 2008). They are found mostly the Western Alps has been found to be within the range within the Sesia-Lanzo and Combin Units North of the 34-30 Ma (Krummenacher & Evernden, 1962; Carraro & Canavese Line (Fig. 7). It has been argued that these Ferrara, 1968; Hunziker, 1974), which is coeval with the dykes are the hypabissal manifestation of a more intense peak of post-collisional magmatism of the entire Alps volcanic activity, nowday totally removed, witnessed by (von Blanckenburg et al., 1998). the occurrence of calc-alkaline to shoshonitic volcano- Ultrapotassic rocks of the western Alps have a lamp- sedimentary unit in the internal portion of the cover ser- roitic affinity; they are plagioclase-free micaceous dykes ies of the Sesia Zone (Callegari et al., 2004). The Traver- characterised by intersertal textures with phlogopite, cli- sella, Valle del Cervo and Biella calc-alkaline plutonic nopyroxene, and K-feldspar, accompanied by minor al- rocks are though to represent shallow level intrusion of tered olivine, and riebckite-arfvedsonite amphibole with the differentiated magmas derived by the calc-alkaline to accessory apatite, sphene, and Fe-Ti oxides (Venturelli et shoshonitic parental magmas (Callegari et al., 2004). al., 1984). Shoshonitic to high-K calc-alkaline plagio- Figure 7. Distribution of Oligocene ultrapotassic dykes and clase-bearing lamprophyric rocks (kersantite to spessar- related sub-volcanic bodies in Western Alps. tite) are found associated in space and time with ultrapotassic rocks. The lamproite-like samples have consistently high MgO contents (8.6-13.6 wt. %; Venturelli et al., 1984; Peccerillo & Martinotti, 2006; Owen, 2008; Prelevic et al., 2008; Conticelli et al., 2009a) (Table 2). In the SiO2- K2O diagram (Peccerillo & Taylor, 1976; Fig. 8b) they plot on its top end, within the ultrapotassic rock field with a positive correlation between K2O and silica, but not with MgO (Conticelli et al., 2009a). Shoshonitic rocks have strongly variable MgO content (1.9-10.9; Venturelli et al., 1984; Peccerillo & Martinotti, 2006; Owen, 2008; Prelevic et al., 2008; Conticelli et al., 2009a), which well correlate with silica and K2O. High-K calc-alkaline rocks show also fairly variable MgO (1.1-7.6; Venturelli et al., 1984; Peccerillo & Martinotti, 2006; Owen, 2008; Prelevic et al., 2008; Conticelli et al., 2009a), with data plotting on the potassium-rich basaltic andesite to rhyolite fields. Low-K calc-alkaline rocks Oligocene ultrapotassic dykes and related sub-volcanic bodies occurr in the Western Alps in the area have been found by Owen (2008). between Val d’Aosta and Piemonte Region and developed in the forms of dyke but some plutonic bodies

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Figure 8. Classification and incompatible trace element diagram with reported the grid for orogenic volcanic characteristics of Western Alps Oligocene ultrapotassic rock suites (Peccerillo & Taylor, 1976). C) Incompati- and related rocks ble trace element patterns for mafic volcanic rocks normalised to the primordial mantle values of Sun & McDonough (1989). Data from Venturelli et al. (1984); Peccerillo & Martinotti (2006); Owen (2008); Prelevic et al. (2008); Conticelli et al. (2009a).

The Western Alps ultrapotassic (lamproite-like) and related rocks are variably enriched in incompatible trace elements, which positively correlate with K2O at almost constant high MgO contents (Conticelli et al., 2009a). These rocks on the Total Alkali Silica diagram (TAS, Le Maitre et al., 2002) align along three different trends at different alkali contents (Fig. 8a), as well as on the K2O vs SiO2 diagram (Fig. 8b). Lamproites have the highest levels of incompatible trace elements, including lantha- nides, but with characteristic fractionation of large ion lithophile elements (LILE) with respect to high field strength elements (HFSE). Passing from ultrapotassic to high-K calc-alkaline mafic rocks, through shoshonites, no significant deviations from this behaviour are observed but just a total decrease of incompatible trace element abundances (Fig. 8c). Throughs at Ba, Ta, Nb, and Ti with peaks at Th, U and Pb are the most important characteristics that are typical of the incompatible trace element distributions of orogenic type magmas (e.g. Hoffman, 1995; Hoefs, 2010). Among HFSE it is worth- noting the normalized Ta/Nb > 1, coupled to the normalized Nd/Sr > 1 that inverted to a value < 1 passing from lamproite to shoshonitic and calc-alkaline rocks (Fig. 8c).

The Miocene Magmatic events of the Western Tyrrhenian Magmatic Province (Corsican) Miocene ultrapotassic, shoshonitic and high-K calc- alkaline igneous rocks are found in close temporal association distributed along the Eastern margin of the Sardi- nia-Corsica micro-plate, although a small monogenetic volcano at Zenobito volcano was produced during the Classification and geochemical characteristics of the Pliocene (Fig. 9). Ultrapotassic rocks, with lamproitic af- Western Alps leucite-free ultrapotassic and associ- finity, are found in the Northeastern portion of the Corsi- ated rocks. A) Total Alkali-Silica (TAS - Fields are: 1 = picritic basalt, 2 = basanite/tephrite, 3 = foidite (leuci- ca Island, 15 km north of Bastia, in the form of a sill in- tite, haüynite, nephelinite, kalsilitite, etc.), 4 = basalt, 5 truded into the Alpine terranes belonging to the “Schistes = potassic trachybasalt; 6 = phonolitic tephrite, 7 = Lustrés” (i.e., Serie of the Castagniccia; e.g., Velde, basaltic andesite, 8 = shoshonite, 9 = tephritic phono- 1967; Wagner & Velde, 1986; Peccerillo et al., 1988); lite, 10 = andesite, 11 = latite, 12 = phonolite, 13 = dacite, 14 = trachyte/trachydacite, 15 = rhyolite) classifi- shoshonitic to high-K calc-alkaline sub-volcanic to vol- cation diagram (Le Maitre, 2002). For TAS field names canic rocks are found few kms offshore from Sardinia see text; B) K2O wt.% vs. SiO2 wt.% classification and Corsica islands, at Sarcya seamount (Cornacya) and

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Capraia Island, respectively (e.g., Mascle et al., 2001; shoshonites are from submarine centers offshore of Chelazzi et al., 2006; Conticelli et al., 2007, 2009a, the southeastern edge of Sardinia Island. High-K calc- alkaline are from the Capraia volcano, located within 2011a; Gasparon et al., 2008; Avanzinelli et al., 2009). the northen Tyrrhenian Sea (Conticelli et al., 2011a). The Punta dello Zenobito volcano is a small monogenetic center lying on the southwestern edge of the Capraia Is- The oldest sampled product of the Corsica Magmatic land, and it is made up by a cinder cone and few lava Province is the Sisco lamproite: one whole rock, one K- flows. feldspar and two phlogopites of different grain-size, for a total of six analyses, have been used to calculate a K/Ar Figure 9. Distribution of Miocene ultrapotassic igneous isochron plot of 14.58 ± 0.2 Ma (Civetta et al., 1978). rocks (dykes and volcanic rocks) and associated 40 39 shoshonites and calc-alkaline rocks from western Mascle et al. (2001) report a Ar- Ar total age of 12.6 ± Tyrrhenian Sea (Corsica Magmatic Province) 0.3 Ma (± 1s) for a dredged andesitic pebble from Corna- cya. This age was calculated from 15 in-situ 40Ar-39Ar analyses performed on a single automorph crystal of biotite; a weighted average calculation on the same data points, carried out in this paper, gives an age of 13.07 ± 0.5 Ma (95% conf. lev., MSWD=1.5), slightly older but equal within error to the total age. It is worth to note that both Sisco and Cornacya age data are related to a unique sample, hence there aren’t data that allow to infer the time span of magmatic activity, if any. The dating of volcanic products of Capraia Island dis- plays a noticeable disagreement among K/Ar, Ar-Ar and Rb/Sr data. Whereas K/Ar (9.8-5.0 Ma: Borsi, 1967; Pierattini, 1978) and Rb/Sr biotite-whole rock data (6.9-3.5 Ma: Barberi et al., 1986, abstract only) evidence a quite long volcanic history, Ar-Ar data (Gasparon et al., 2009) show that the majority of the actually subaerial samples are comprised in a narrow interval of time (7.8-7.2 Ma). Age data related to Punta dello Zenobito monogenetic volcano, whose orogenic affinity has been questioned (Chelazzi et al., 2006; Conticelli et al., 2007, 2009a, 2011a) disagree as well. K/Ar and Ar-Ar data are quite concordant within error (4.93 Ma, Borsi, 1967, and 4.76 Ma, Gasparon et al., 2009, respectively), while either the 2.72 Ma K/Ar datum of Pierattini (1978) or the 3.92 Ma Rb/Sr datum of Barberi et al. (1986) are younger. Ar-Ar ages are on average preferred relative to K/Ar model ages, but the spread registered also by Rb/Sr biotite ages might be indicative of hidden problems in dating Capraia samples. The Sisco lamproite is a leucite- and plagioclase-free ultrapotassic rocks with intersertal texture and a parageneses made of phlogopite, clinopyroxene, olivine, sanidine, and K-richterite associated to subordinate abundance of chromian spinel, ilmenite, pseudobroockite and priderite. Rare roedderite has also been found. Si+Al tet- Ultrapotassic rocks are found exclusively along the rahedral deficiency has been also observed in the chain northeastern edge of the Corsica island, whereas

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The Pliocene-Pleistocene Magmatic events: been also produced (Poli et al. 1984, 1989; Peccerillo et Tuscan Magmatic Province al., 1987; Pinarelli et al., 1989; Poli 1992, 1996; Wester- The Tuscan Region has been the site of bimodal igne- mann et al., 1993; Gagnevin et al., 2004, 2005a, 2005b; ous activity during the Pliocene and Pleistocene (Fig. Poli et al., 2004). For the purpose of the present work we 11). Crustal-derived magmas, formed by anatexis of low- are not going to include here igneous rocks that are gen- er to intermediate continental crust occurred to form erated dominantly by magmas of continental crust deriva- granitic to granodioritic plutonic bodies (Fig. 11) and tion. They are usually treated separately from mantle de- some hybrid products that have intermediate characteris- rived ultrapotassic and related rocks. tics between mantle- and crustal-derived magmas have

Figure 11. Distribution of Plio-Pleistocene ultrapotassic igneous rocks and associated shoshonites and calc-alkaline rocks from Eastern Tyrrhenian Sea and Italian Peninsula (Tuscan, Roman and Lucanian Magmatic Provinces)

Ultrapotassic rocks are found distributed along the Tyrrhenian border of the Italian peninsula, and in some cases offshore within the eastern Tyrrhenian Sea and on the other hand in the intra-apennine setting. Tuscan, Roman and Lucanian magmatic provinces can be efficiently divided on the basis of mineralogy of the ultrapotassic rocks, timing of magmatism and location with respect to the Italian peninsula. Tuscan Magmatic rocks are Pliocenic in ages and ultrapotassic terms are always leucite-free; they are distributed in the westernmost portions of the region. Roman Magmatic rocks are Pleis- tocenic to holocenic in ages and ultrapotassic terms are always leucite-bearing; they are distributed in the central portions of the region. Lucanian Magmatic rocks are Pleistocenic in ages with leucite/haüyne-bearing ultrapotassic terms; they are distributed locally in the southeasternmost area of the the region. The only deviation from this rule is represented by the Monte Amiata volcano. See text for further explanation. Redrawn after Avanzinelli et al. (2009); Mattei et al. (2010).

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The Pliocene mantle-derived ultrapotassic and related and new analyses with the use of mixed mineral phases rocks are made up by high-potassium calc-alkaline, by Lombardi et al. (1974), as testified by K-feldspars shoshonitic, and plagioclase- and leucite-free alkaline ul- non-stoichiometric K contents. A fairly young age, 2.36 trapotassic rocks (i.e., lamproite) generated by magmas Ma, on a sanidine with a stoichiometric K% is reported of ultimate mantle-origin (Conticelli et al., 2009a). They also by Evernden & Curtis (1965). The data since now are found as scattered outcrops straddling the Tyrrhenian available do not allow to identify a precise time length border of the Italian Peninsula (Fig. 11). Traditionally the for this volcanism. Tuscan Magmatic Province has been considered to be The Pontine Islands are placed offshore of the South- confined a little beyond the administrative border of the ern Latium coast (Fig. 11). Ponza and Ventotene Islands Tuscany region (Peccerillo et al., 1987; Innocenti et al., are placed at the same distance from the Apennine front 1992; Poli et al., 2004), but coeval leucite-free potassic of Tolfa-Manziana-Ceriti dome comeplexes, due to the to sub-alkaline magmatic rocks are found along the entire arcuate morphology of the Northern Apennine chain. On- Tyrrhenian border of the peninsula (Avanzinelli et al., ly K/Ar data are available in literature for the Pontine Is- 2009). Therefore, in this chapter we have also included lands volcanic rocks. The recent paper by Cadeaux et al. the descriptions of the coeval volcanic rocks that have (2005) gives an age interval from 4.2 to 3.7 Ma for the been either intruded and erupted few kms north of Rome outcropping rhyolitic dykes and associated hyaloclastites (i.e., Tolfa, Manziana, Ceriti; Fig. 11), and offshore at of Ponza Island. Previous authors indicate older ages for Ponza Island, within the Pontinian Archipelago (Fig. 11). the same products (5.1-4 Ma: Barberi et al., 1967; Savel- Indeed these volcanic rocks have high-K calc-alkaline li, 1983, 1988; Altaner et al., 2003). Cadeaux et al. and shoshonitic affinities, although silicic terms prevail (2005) recognise a second episode at about 3 Ma in the over mafic ones. central-southern part of the island, and indicates an age The oldest volcanic rocks of the Tuscan Magmatic around 1 Ma for the final subaerial activity of the South- Province are found at Elba Island, Tuscan Archipelago ern portion of the Island. Barberi et al. (1967) and Savelli (Fig. 11) with an 40Ar-39Ar age of 5.8 Ma (Conticelli et (1988) report slightly older ages for the final activity of al., 2001), followed by the emplacement in the mainland, Ponza. Furthermore, K/Ar ages of illite-smectite of hy- Val d’Era area, of the hypabissal minette of Montecatini drotermally altered rocks constrain the alteration event at Val di Cecina, 4.2 Ma (K/Ar; Borsi et al., 1967), of the about 3.4 Ma (Altaner et al., 2003). At Palmarola Island orendite of Orciatico (4.1 Ma, Capaldi G. Personal Com- K/Ar ages obtained from different laboratories are less munication in Conticelli et al., 1992) (Fig. 11), and of the discordant than in Ponza, and are comprised between olivine latitic dikes at Campiglia (Conticelli, 1989). Al- 1.8-1.6 Ma (Barberi et al., 1967; Savelli, 1988) and most coevally are erupted the products of the Tolfa-Man- 1.6-1.5 Ma (Cadeaux et al., 2005). The Ventotene Island ziana-Ceriti dome complexes (Fig. 11). They are made is the subaerial remnant of post caldera volcanic rocks up of trachytic to rhyodacitic domes, massive lava flows, emplaced along an old calderic rim. The Ventotene stra- and welded ignimbrites, but latitic to olivine latitic mafic tovolcano is well below sea level. K/Ar ages on Vento- enclaves are also found to testify the occurrence of mafic tene oldest outcropping products disagree, ranging from magmas in their genesis (Fazzini et al., 1972; Clausen & 1.75 Ma (Barberi et al., 1967) to 0.92 Ma (Bellucci et al., Holm, 1990; Pinarelli, 1991; Bertagnini et al., 1995). 1999); the volcanic activity then continues till an unde- Several K/Ar dates are available for the Tolfa-Manziana- fined recent time (< 0.15 Ma for a pumice form the up- Ceriti volcanic rocks spread from 4.3 to 1.9 Ma, exclud- permost pyroclastic floe unit, Metrich et al., 1988). Santo ing a datum from a xenolith (Evernden & Curtis, 1965; Stefano Island appears as a lava dome, emplaced on a Bigazzi et al., 1973; Lombardi et al., 1974; Villa et al., flank of Ventotene submerged sratovolcano, which is 1989). Villa et al. (1989) performed a new mineral sepa- covered by pyroclastic products: K/Ar model ages are ration on four rocks previously analysed by Lombardi et comprised between 1.2 and 0.6 Ma (Barberi et al., 1967; al. (1974), and obtained ages overlapping within error for Fornaseri, 1985a; Metrich et al., 1988; Bellucci et al., Tolfa and Manziana samples, all around 3.5 Ma, either 1999). A bit more southeast, in the Campanian Plain older (3) and younger (1) than previous data. Villa et al. (Fig. 11), thick sequences of altered volcanites of calc-al- (1989) explain the discrepancies observed among the old kaline affinity were found in drillings (Parete 2 and Villa

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Literno 1 wells; Di Girolamo et al., 1976). K/Ar age of 1976). C) Incompatible trace element patterns for maf- the deepest sample of Parete 2 well (2.0 ± 0.4 Ma, Bar- ic volcanic rocks normalised to the primordial mantle values of Sun & McDonough (1989). Data from Met- bieri et al., 1979) is devoid of analytical details. rich et al. (1988); Peccerillo et al. (1988); Pinarelli 40Ar-39Ar analyses of plagioclases separated from both (1991); Conticelli & Peccerillo (1992); Conticelli et al. wells failed to give reliable results (Brocchini, 1999). (1992, 2002, 2007, 2009a, 2011b, 2011c); Conticelli (1998); D’Antonio et al. (1989a); Cadeaux et al. (2005); Hence, the age of this volcanism remains uncertain. Prelevic et al. (2008). Figure 12. Classification and incompatible trace element characteristics of Tuscan Magmatic Province The youngest Leucite-free ultrapotassic rocks of the Tuscan Magmatic Province are found a bit more east, erupted along the NNW-SSE extensional basin that will be occupied later, during the Pleistocene, by the Roman leucite-bearing volcanic rocks. The emplacement of the basaltic andesitic to shoshonitic lavas of Radicofani center (Fig. 11) is placed around 1.3 Ma: the 40Ar-39Ar age of one Radicofani lava flow and the K/Ar model ages of the neck agree within error (Pasquarè et al., 1983; D'Ora- zio et al., 1991). K/Ar model ages on the olivine latite with lamproitic affinity and latite to trachytes with shoshonitic affinity of Monte Cimino Volcanic Complex are comprised in the interval 1.43-0.97 Ma (Evernden & Curtis, 1965; Nicoletti et al., 1969; Puxeddu, 1971; Sol- levanti, 1983), partially overlapping with Radicofani volcanic rocks. There are also two 40Ar-39Ar age spectra on a sanidine megacryst from the Faggeta quartz-latitic dome, without a clear age calculation (Villa, 1988: the paper was centered on Ar geochemistry). The flattish parts of the two spectra give a weighted average of about 1.1 and 1.16 Ma (new calculation from Table 1 of Villa, 1988). Only a K/Ar model age of 0.82 Ma is available for the olivine latite with lamproite affinity of Torre Alfina (Nicoletti et al., 1981a; Conticelli, 1998). The rocks of this period range in composition from ultrapotassic (i.e., lamproite-like) to shoshonitic and high- K calc-alkalic rocks (Table 3; Fig. 12b). Shoshonitic rocks are represented by the overall spectrum of compositions, from trachybasalt to trachyte, as well as high-K calc-alkalic rocks with terms ranging from high-K basaltic andesites to rhyolites (Fig. 12a). Lamproite-like rocks are few and mostly mafic with phenocrysts of Al-poor clinopyroxene, and olivine with chromite inclusions (Fig. 3a-c), set in a groundmass made up of clinopyroxene, phlogopite, sanidine, K-richterite, apatite, picroilmentite and Ti-magnetite and accessory perrierite/chevkinite Classification and geochemical characteristics of Tus- can Plio-Pleistocene ultrapotassic (lamproites) and re- (Wagner & Velde, 1986; Conticelli et al., 1992; Cellai et lated rocks. A) Total Alkali-Silica (TAS) classification al., 1993, 1994; Conticelli, 1998). The aluminium con- diagram (Le Maitre, 2002). B) K2O wt.% vs. SiO2 wt.% tent in clinopyroxene increases from lamproite to shosh- classification diagram with reported the grid for onite with contemporaneous appearance of plagioclase orogenic volcanic rock suites (Peccerillo & Taylor,

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(Fig. 3d; Conticelli et al., 2010b). Two pyroxene high-K conclusion and affirm that sanidine ages are “magmatic calc-alkaline rocks are strongly differentiated products, at ages” and not eruption ages, leading to uncertain age as- Cimino, Tolfa, Manziana, and Ponza, which are associ- signment for all products. In spite of disputes on the time ated at younger mafic lamproite-like shoshonitic rocks length of Amiata activity, this volcano is much younger (Clausen & Holm, 1990; Pinarelli, 1991; Perini et al., of any other volcanic center belonging to the Tuscan 2003; Conte & Dolfi, 2002; Paone, 2004; Cadeaux et al., Magmatic rocks (leucite-free ultrapotassic rocks) and 2005; Conticelli et al., 2010d). Equilibrium clinopyrox- well within the time span of Roman volcanic rocks (lec- ene and orthopyroxene is the main petrographic charac- ite-bearing ultrapotassic rocks). teristic of the most differentiated terms, which are associated to biotite, sanidine, plagioclase, apatite, zircon, il- Figure 13. Geological sketch map of the Monte Amiata menite, Ti-magnetite. volcano a hybrid volcanic center transitional between Tuscan and Roman Magmatic provinces The mafic Plio-Pleistocene magmatic rocks of the peri-tyrrhenian area positively correlate with K2O contents (see Fig. 8 in Conticelli et al., 2009a), showing a temporal decrease in the contents of this oxide. High- MgO volcanic rocks, irrespectively of their K2O content, display strong depletions in Ti, Ta, and Nb relative to Th and LILE (Fig. 12c). When compared to Corsican rocks, Plio-Pleistocenic volcanic rocks show higher peaks at Th, U, Pb, Zr and Hf, and deeper troughs of Ba, Ta, Nb, P, and Ti (Fig. 12c). These rocks still dispay normalized Ta/ Nb and Nd/Sr lower than unity. Conticelli & Peccerillo (1992) argued that incompatible trace element concentrations and their distribution and fractionation are primary characteristics derived directly from their mantle source(s) due to sediment recycling within the upper mantle. Geological sketch map of the Monte Amiata linear volcano. Redrawn after Ferrari et al. (1996). The Monte Amiata: a Quaternary “hybrid” volcano The Monte Amiata volcanic rocks range from Two- The Monte Amiata volcano, Late Pleistocene in age, Pyroxene trachydacites to olivine-bearing, orthopyrox- is located in Southern Tuscany, well within the area of ene-free olivine latite to trachyte (Fig. 14a) (Ferrari et al., the Tuscan Magmatic Province (Fig. 11). The Monte 1996). The oldest products belonging to the Basal tra- Amiata volcano is a small linear volcano that produced chytic complex are made up of biotite, plagioclase, sani- few lava flows, domes and dome collapse (Fig. 13) with dine, clinopyroxene and orthopyroxene, amphibole, Ti- a high-K calc-alkaline to shoshonitic character (Fig. 14). magnetite and rarely by interstitial quartz (van Bergen, Its chronology relies on several K/Ar and Fission Tracks 1984; Ferrari et al., 1996). The youngest ones have a data that cover the whole volcanic activity (Evernden & slightly bimodal composition with early emplacement of Curtis, 1965; Bigazzi et al., 1981; Pasquaré et al., 1983; trachytic to latititic lavas (Fig. 14a), in the form of exoge- Cadeaux & Pinti, 2009), and few 40Ar-39Ar data on the nous lava domes and short massive lava flows, and the fi- oldest products (Laurenzi & Villa, 1991; Barberi et al., nal emplacement of olivine-latitic to shoshonitic lava 1994). The initial known activity start at about 300 ka flows (Fig. 14a). In addition Monte Amiata volcanic (Barberi et al., 1994; Cadeaux & Pinti, 2009), hence all rocks are characterised by the occurrence of abundant older ages reported in literature are problematic. The end magmatic enclaves and metasedimentary xenoliths rang- of Amiata volcanic activity is quite undefined: Bigazzi et ing from centimetre to decimetre size. Metasedimentary al. (1981) gave ages around 200 ka for the final lava xenoliths, ranging from angular to irregularly-rounded, domes, but Cadoux & Pinti (2009) dispute that are mostly flattened in shape and predominate in Basal

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Trachydacitic rocks. Fine-grained magmatic enclaves a “hybrid” volcano due to the interaction between leu- have ellipsoidal shape with cuspidate margins convex to- cite-free and -bearing potassic to ultrapotassic magmas ward the hosts. The amount of fine-grained magmatic en- (Conticelli et al., 2009c). claves increases with decreasing ages of host rocks, from Basal Trachytic Complex to Final Lavas. Fine-grained Figure 14. Classification and incompatible trace element magmatic enclaves range from porphyritic to aphyric and characteristics of Quaternary Monte Amiata volcanic rocks invariably display chilled margin texture, ranging in compositions from trachybasaltic to shoshonitic and latitic. Petrographic and compositional characteristics of fine- grained magmatic enclaves suggest that they were molten at the moment of the inclusion by the host trachytic magma. Their characteristics are strongly suggestive for the occurrence of interaction between different types of magmas prior to eruption (Ferrari et al., 1996; Cadoux & Pin- ti, 2009). This hypothesis is also supported by the occurrence of disequilibria texture among the mineral assemblages of the dome complex (intermediate volcanic activity) (Fig. 3e). From a petrological point of view the Monte Amiata volcanic rocks were produced by the crystallization of strongly differentiated shoshonitic magma with trachytic to trachydacitic compositions (Ferrari et al., 1996; Ca- doux & Pinti, 2009; Conticelli et al., 2009c). This magma produced the early eruption of the basal trachytic complex and of the trachytic to latitic dome complex (Fig. 14a). Conticelli et al. (2009c, 2010b) suggested that the early Monte Amiata magma derived by the fractional crystallization plus crustal contamination starting from a parental magma similar in composition to the Radicofani shoshonitic trachybasalt. The intermediate and final eruptions of the Monte Amiata have been produced by the mingling between this extremely differentiated high silica magma and ultrapotassic silica-undersaturated magmas (Roman) (van Bergen et al., 1983). The arrival in the shallow level magmatic reservoir of newly formed leucite-bearing hot magma from the source region triggered Monte Amiata eruptions. Mafic enclaves represent the evidence of the mingling between leucite-bearing Roman magmas and the relic high-K calc-alkaline magmas of the previous Tuscan episode. Leucite crystallization from Roman magma has been suppressed by the strong silica activity of the stagnant differentiated Tuscan magmas, Classification and geochemical characteristics of the crystallizing in the magma reservoir at shallow depth. Monte Amiata volcanic rocks and mafic enclaves. A) Total Alkali-Silica (TAS) classification diagram (Le Mai- These processes well explain the characteristic composi- tre, 2002). B) K2O wt.% vs. SiO2 wt.% classification tion of the Monte Amiata rocks and the very young time diagram with reported the grid for orogenic volcanic span of volcanic activity, suggesting that the Monte rock suites (Peccerillo & Taylor, 1976). C) Incompati- Amiata is neither a Tuscan nor a Roman volcano, but just ble trace element patterns for mafic volcanic rocks normalised to the primordial mantle values of Sun &

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McDonough (1989). Data from Ferrari et al. (1996), The Roman Magmatic Province and authors’ unpublished data. The Roman Magmatic Province comprises several The mingling hypothesis is also testified by the in- volcanic districts that can be made up by a cluster of two/ compatible trace element distribution shown in figure three volcanic apparata (e.g., Vulsini, Sabatini, and Nea- 14c. Indeed mafic Final Lavas display normalized pat- politan, Fig. 11), by a monogenetic volcanic field (e.g., terns very similar to those of the Tuscan rocks, with Middle Latin Valley, and Campi Flegrei, Fig. 11), or just troughs at Ba, Ta, Nb, P, and Ti, and peaks at Cs, U, and by a single volcanic apparatus with a summit caldera and Pb. The strong peak at U with extremely high U/Th ratios a post-caldera monogenetic activity (e.g., Vico, Colli Al- is peculiarly different, and it is much higher than in the bani, and Roccamonfina volcanoes, Fig. 11). The Roman rest of the Tuscan rocks (Fig. 14c). Incompatible trace el- Magmatic Province, in Northern Latium, overlaps the ement patterns of mafic enclaves differ greatly from volcanic rocks belonging to the Tuscan Magmatic Prov- those of the lavas in terms of normalized Ta/Nb, Nd/Sr, ince (Fig. 11). The volcanism of the Roman Magmatic and Zr/Hf, although no differences have been observed Province begun at about 760 ka (Florindo et al., 2007) among U/Th ratios (Fig. 14c). and protracted till the present time, being the last eruption at Vesuvius of 1944 A.D., with a maximum produc- The Quaternary Magmatic events: Roman tion of volcanic rocks between 400 and 200 ka in the Lat- and Lucanian Magmatic provinces ian districts and between 200 ka and the present for the Early in the twentieth century, Washington (1906) de- Neapolitan district. Minor centers of the Roman Magmat- fined the Roman Magmatic Province as a unique mag- ic Province are found in Umbria, in an intramontane re- matic association characterized by leucite-bearing ultra- gion, at San Venanzo and Cupaello. potassic volcanic rocks, extending from Northern Latium to the Neapolitan area. Since then several authors re-de- The Latian districts fined the Roman Province limits on the basis of different The Latian volcanic districts occupy prevalently the criteria (e.g., Hawkesworth & Vollmer, 1979; Vollmer & Latium region although the Roccamonfina volcano is Hawkesworth, 1980; Ayuso et al., 1998; Paone, 2004; well within the campanian region. They have been active Peccerillo, 2005a). In the present paper we keep the orig- coevally during the Pleistocene and presently most of inal definition using the petrographic criterium adopted them are just quiescent. On the basis of petrographic data by Washington (1906) and later resurrected by Turner & the Latian districts are prevalently made up by leucite- Verhoogen (1960), because this is coherent with an easy bearing ultrapotassic magmas, in some cases preceeded recognition from other timely close volcanic association by hybrid Tuscan-Roman magmas, as in the cases of ear- worldwide, and because this division correlates with ly activity at Vulsini, Vico, Sabatini (see below), and fol- main mechanisms of magma genesis and geodynamic lowed by less alkaline leucite-bearing and leucite-free events in the area (Conticelli et al., 2004; Avanzinelli et shoshonitic volcanic rocks in the post caldera activity. al., 2009). Indeed the Roman Province is characterized The Leucite-bearing ultrapotassic magmas are predomi- by Pleistocene to Holocene leucite-bearing ultrapotassic nat over the late leucite-free magmas (i.e., shoshonitic to igneous rocks, whereas the Tuscan Magmatic Province calc-alkaline magmas; Avanzinelli et al., 2009, and refer- by Pliocene to Pleistocene leucite-free ultrapotassic igne- ences therein). ous rocks, the Lucanian Magmatic Province by Pleisto- 1. Vulsini district cene haüyne/leucite-bearing ultrapotassic rocks. This The Vulsini district is the northernmost volcanic clus- would be a simple, but consistent, criterium to assess ter of the Roman Province and it is formed by the coales- magmatic domains. With an eye to the geochemical and cence of four large volcanic apparata: the Palaeo-Bolse- isotopic characteristic we further divide internally the na, Bolsena, Montefiascone and Latera volcanoes (Nappi Roman rocks between the Latian districts, in which ultra- et al., 1987, 1998; Palladino et al., 2010) (Fig. 15). The 2 potassic leucite-bearing volcanic rocks dominate over volcanic rocks cover an area larger than 2,000 km , fill- shoshonites, and the Neapolitan one, where shoshonite ing up a depressed area represented by the Siena-Radico- volcanic rocks are more abundant than ultrapotassic fani and Paglia-Tevere grabens. The coalescence of the leucite-bearing volcanic rocks (Fig. 11). four volcanic apparatus formed a shield-like area with a

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 26 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ central depressed zone occupied today by the Bolsena 40Ar-39Ar dating performed on a new mineral separation lake (Fig. 15). All four volcanic complexes are made up from the original six samples of Barberi et al. (1994) mainly of ignimbrites with subordinate lava flows, al- gives a well constrained age for this formation of 0.498 though a lava plateau has been recorded in the early his- Ma (Laurenzi & Deino, 1996). The Bolsena volcanic tory of the Latera volcano (e.g., Conticelli et al., 1987, complex begun its activity after the formation of the Pa- 1989; Vezzoli et al. 1987). laeo-Bolsena caldera and lasted for few hundred thousand years (Palladino et al., 2010, and references inclu- Figure 15. Geological sketch map of the Vulsini district ded). It developed mainly in the eastern sector of the Vul- (Roman Magmatic Province). sinisan district with the formation of a large caldera depression partly occupied by the Bolsena Lake, and produced two thick ignimbrite sheets, fall deposits and lava flows which built an ignimbrite shield (Freda et al., 1990; Nappi et al., 1998; Palladino et al., 2010). Fissural lava flows formed a lava plateau south of Bolsena Lake in the Marta-Tuscania area (Palladino et al., 1994). The Monte- fiascone volcano (~0.29 - ~0.23 Ma: Nappi et al., 1995; Brocchini et al., 2000) evolved within the period of activity of Bolsena and partially overlapped with the Latera Volcano, developed in the western sector (~0.28 - ~0.15 Ma: Metzeltin & Vezzoli, 1983; Turbeville, 1992). Both Montefiascone and Latera volcanoes are characterized by different activities that brought to the formation of a small stratovolcano with a small summit caldera (ca. 2.5 Geological sketch map of the Vulsini district. Legend: 1) Holocene alluvial and lacustrine deposits; 2) traver- km wide) at Montefiascone, compared to a large flat ig- tine; 3-9) Bolsena, Latera and Montefiascone calde- nimbritic volcanic plateau with a large central polyphasic ras; 3) scoria cones; 4) phreatomagmatic deposits; 5) nested caldera (ca. 9 km wide) at Latera (Sparks, 1975; leucite-bearing lavas; 6) pozolanaceous ignimbrites; 7) Varekamp, 1980; Conticelli et al., 1986, 1987, 1991; fallout and reworked pyroclastics; 8) spatter-rich ignimbrites; 9) lithoidal ignimbrites; 10) PaleoBolsena Vezzoli et al., 1987; Coltorti et al., 1991; Turbeville volcano welded to unwelded ignimbrites and leucite- 1992, 1993; Di Battistini et al., 1998, 2001). The final ac- bearing tuffs; 11) rhyodacite Peperino Tipico ignim- tivity is represented by the Bisentina and Martana Is- brite (Cimini dome complex); 12) rhodacitic domes; 13) post-orogeny Pliocene-Pleistocene marine sedi- lands, and likely other centers below the Bolsena Lake, ments; 14) Allochtonous Flysch; 15) Meso-Cenozoic tentatively still active around 0.13 Ma (K/Ar, Nappi et pre-syn-orogenic successions; 16) Paleozoic base- al., 1995). ment; 17) caldera. The volcanic products are mainly characterised by Palaeo-Bolsena volcanic apparatus has been supposed leucite-bearing ultrapotassic rocks (Tables 4 and 5) with to be the oldest volcanic center and it is made up by the few leucite-free shoshonitic rocks confined in the post- large trachytic, partly welded, ignimbrite called “Nen- caldera activity of the Latera volcano (Table 6; e.g., Con- fro”, associated to leucititic to tephri-phonolitic lava ticelli et al., 1991) and some melilite-bearing leucitites flows and plinian pyroclastic fall horizons (Nappi et al., (kamafugites) in the early stages of the Montefiascone 1987, 1991, 1994, 1995). Volcanic activity begun with a volcano (di Battistini et al., 2001). plinian fall layer dated at 0.59 Ma (40Ar-39Ar, Barberi et The ultrapotassic rocks range in composition from al., 1994) and 0.58 Ma (K/Ar, Nappi et al., 1995). Sever- leucite-bearing basanites, leucitites, tephrites, phonolitic- al conflicting age data are published on “Nenfro” ignim- tephrites, tephritic-phonolites, and phonolites (Fig. 16a). brite that likely caused the Paleo-Bolsena calderic col- Extremely differentiated products dominated volumetri- lapse: 0.88 to 0.4 Ma (K/Ar, Nicoletti et al., 1981), 0.5 cally over mafic terms, but in some cases syn-depositio- Ma (40Ar-39Ar, Barberi et al., 1994) and 0.51 Ma (K/Ar, nal formation of analcite after leucite allow the K2O and Nappi et al., 1995). Single crystal, laser total fusion alkalis loss, a characteristic capable to drive the juvenile

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Figure 16. Classification and incompatible trace element clasts (pumice) in ignimbrite toward a trachy-phono- characteristics of Pleistocene volcanic rocks from Monti litic to trachytic compositions (Conticelli et al., 1987; Vulsini volcanoes. Parker, 1989) (Fig. 16a). The most mafic compositions are always found among lava flows and they are found mainly in the plateau-like structure of the southern sector of the Vulsinian district and of Montefiascone volcano where leucite-bearing basanitic to tephritic lavas do occur (Civetta et al., 1984; Rogers et al., 1985; Conticelli et al., 2002). Post caldera activity was particularly intense at the Latera volcano with bimodal magmatism both leucite- bearing and –free lavas (Fig. 15). Leucite-bearing post- caldera Latera lavas have compositions ranging from tephritic to tephri-phonolitic (Fig. 16a), whereas leucite- free lavas are particularly abundant within and external to the caldera in the southern eastern sector of the volcano with the Selva del Lamone lava flow (Fig. 15) and they have a clear shoshonitic affinity with lavas ranging in composition from K-trachybasalts to latites (Figs. 16a,b). The shoshonitic trachy-basalts have mineralogy assemblages made up of abundant olivine, clinopyroxene and plagioclase, but they differ significantly in terms of geochemistry with respect to other post-caldera shoshonitic rocks from other volcanic districts of the Roman Province (e.g., Holm et al., 1982; Varekamp & Kalamar- ides, 1989; Conticelli et al., 1991, 2009b; Turbeville, 1993). The most abundant mafic mineral in the Roman rocks is the clinopyroxene, which differ significantly from volcanic rocks crystallized in equilibrium with leucite or not. Indeed, clinopyroxene from lamproite-like ultrapotassic rocks are generally aluminium poor, with Si +Al not sufficient to fill completely the tetrahedral site, whereas clinopyroxene from Roman rocks, either leucite- free or –bearing ones, are characterized by excess Al that patitioned between tetrahedral and octahedral sites (Bar- ton et al., 1982; Holm, 1982; Cellai et al., 1994; Bindi et al., 1999; Chelazzi et al., 2006). Clinopyroxene in shoshonite from Latera volcano are transitional between those Classification and geochemical characteristics of the typical of leucite-free (Tuscan lamproites) and Roman Vulsini leucite-bearing ultrapotassic rocks and associ- rocks, whereas those from shoshonites in other Roman ated shoshonitic ones. A) Total Alkali-Silica (TAS) districts have also Al excess (Perini & Conticelli, 2002; classification diagram (Le Maitre, 2002). B) K O wt.% 2 Boari & Conticelli, 2007; Cellai et al., 1994). Leucite is vs. SiO2 wt.% classification diagram with reported the grid for orogenic volcanic rock suites (Peccerillo & found both as phenocryst and as groundmass phase in Taylor, 1976). C) Incompatible trace element patterns plagioclase leucitites and leucitites (Fig. 3h). Sanidine is for mafic volcanic rocks normalised to the primordial mantle values of Sun & McDonough (1989). Data from present both in the most evolved phonolitic and trachy- Holm et al. (1982); Civetta et al. (1984); Rogers et al. phonolitic terms, and it is also found also in leucite-free (1986); Conticelli et al. (1987, 1991, 2002, 2007); Col- rocks of the Palaeo-Bolsena volcano and of the post-cal- torti et al. (1991); Di Battistini et al. (2001, 2002); dera Latera volcano. Gasperini et al. (2002).

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Apparently normalized incompatible trace element period): 4) Carbognano phreatomagmatic ignimbrite; patterns of plagioclase leucititic rocks of the Vulsinian 5) caldera forming phonolitic ignimbrites; 6) stratocone building leucite-bearing lavas; 7-9) Cimini dome district are similar to those of earlier magmatisms (Fig. complex (1300-900 ka): 7) rhyodacitic Peperino Tipico 16c) characterized by leucite-free ultrapotassic rocks ignimbrite; 8) rhyodacitic domes; 9) lamproitic lava; (i.e., lamproite) and associated shoshonites and calc-alka- 10) post-orogeny Pliocene-Pleistocene marine sediments; 11) Allochtonous Flysch; 12) Macigno Flysch; line rocks (i.e. Western Alps, Western Tyrrhenian Sea, 13) caldera. Tuscany). Vulsinian plagioclase leucititic rocks and associated shoshonites, however, display larger throughs at The stratigraphy of Vico volcano is divided into three Nb, Ta, and Ti, the appearance of a small through at Hf, main rock successions: the Rio Ferriera, the Lago di Vi- and a small peak at Sr, concomitantly to the inversion of co, and the Monte Venere successions (Perini et al., the U/Th and Ta/Nb normalized ratios (Fig. 16c), with re- 1997, 2004). The early activity, during the Rio Ferriera spect to the older leucite-free ultrapotassic and associated period (Ist) produced pyroclastic fall and flow units inter- shoshonites and calc-alkaline rocks (Figs. 8c, 10c, 12c). bedded to minor lava flows (Cioni et al., 1987; Barberi et 2. Vico district al., 1994; Perini et al., 1997, 2000). The onset of the Rio The Vico district consists of a single Pleistocene vol- Ferriera period is constrained by the age of the basal pli- canic edifice built in the form of a conic stratovolcano nial fall at about 0.42 Ma (Sollevanti, 1983; Barberi et cut by a summit polygenetic caldera (Mattias & Ventri- al., 1994). All K/Ar model ages older than 0.42 Ma (Nic- glia, 1970; Perini et al., 1997, 2004). Post-caldera activi- oletti, 1969) are clearly biased. The Lago di Vico period ty, subordinate in volume, both within and on the edge of (IInd) involved an early stratovolcano-building phase the caldera do occur (Fig. 17; Perini et al. 1997, 2004). (0.30–0.26 Ma; Sollevanti, 1983; Laurenzi & Villa, 1987; The Vico volcano like the other Roman volcanoes North Barberi et al., 1994) with emplacement of leucite-bearing of Rome (Fig. 11) developed within the NW–SE Siena- lava flows (~ 50 km3; Bertagnini & Sbrana, 1986; Perini Radicofani and Paglia-Tevere extensional basin (Barberi et al., 1997, 2004). Villemant & Fléhoc (1989) report a et al., 1994), and it covers almost completely an older K/Ar age of 0.18 Ma and a U-Th isochron age of 0.21 volcanic apparatus belonging to the Tuscan Magmatic (+0.028/-0.022) Ma for the final episode of the stratovol- Province, the Monte Cimino Volcanic Complex. cano building period. Towards the end of the Lago di Vi- co period four explosive ignimbrite-forming eruptions Figure 17. Geological sketch map of the Vico district (Roman Magmatic Province). caused the destruction of the Vico edifice and the formation of an 8 km diameter polygenetic caldera (Perini et al., 1997, 2004). These were the Farine, Ronciglione (0.16 Ma), Sutri (Tufo Rosso a scorie nere, 0.15 Ma) and Carbognano (0.14 ka) eruptions (Sollevanti, 1983; Lau- renzi & Villa, 1987; Barberi et al., 1994; Perini et al., 1997, 2004; Bear et al., 2009a,b). The post caldera activity (i.e., Monte Venere period - IIIrd) comprises the so called “Tufi Finali”, several monogenetic cones, and mi- nor lava flows. The Monte Venere is an intra-caldera cinder cone, whereas other three cinder cones are found along the northern caldera rim from Poggio Nibbio to Poggio Varo (Fig. 17). A small shoshonitic lava flow has been vented from a fracture on the caldera margin flowing down both into the caldera and along the external northern flank of the volcano (Perini et al., 1997, 2004). K/Ar ages comprised between 0.095 and 0.085 Ma are Geological sketch map of the Vico volcano. Legend: from Monte Venere rocks (Laurenzi & Villa, 1985; Vil- 1) Holocene alluvial and lacustrine deposits; 2) traver- lemant & Fléhoc, 1989); a 40Ar-39Ar age equal within er- tine; 3) Monte Venere period: post-caldera scoria ror to K/Ar ones was obtained on scoriaceous deposits cones (third period); 4-6) Lago di Vico period (second

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 31 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ drilled into the Vico lake sediments (Magri & Sadori, Figure 18. Classification and incompatible trace element 1999; Laurenzi, unpublished datum). characteristics of Pleistocene volcanic rocks from Vico volcano. The Rio Ferriera volcanic rocks have a mild potassic nature, resembling closely previous Tuscan rocks of the underlying Cimino volcano, but leucite appears random- ly. They range in composition from latite to trachyte and rhyodacite (Fig. 18a, 18b). Large sanidine phenocrysts are also found but they are not in equilibrium with Vico magmas, corroborating the hypothesis that Rio Ferriera formations represent hybrid rocks due to magma mixing between differentiated Tuscan high-K calc-alkaline magmas and newly arrived ultrapotassic silica-undersaturated leucite-bearing Roman magmas (Perini et al., 2000, 2003). The Lago di Vico period of activity was dominated by plagioclase-leucititic lavas and pyroclastic rocks, ranging in compositions from leucite-bearing tephrites to leucite-bearing phonolites, passing through phonolitic- tephrites and tephritic-phonolites (Fig. 18a). Syn-depositional alkali loss in pyroclastic rocks is observed at Vico volcano similarly to Vulsinian district (Fig. 18a). Vico post caldera activity, analogously to what observed at Latera volcano, diplays a clear bimodal petrologic affinity (Tables 5 and 6). Leucite-bearing tephrites (Monte Venere scoria and lavas) beside leucite-free olivine latites with a shoshonitic affinity (Poggio Nibbio lavas) and olivine trachybasalts (Poggio Nibbio scoria), the latter showing seldom leucite both as phenocrysts and in the groundmass, occur in the post caldera period (Fig. 18a). Normalized incompatible trace element patterns of leucite-bearing Vico rocks differs significantly from those of Vulsinian ones (Fig. 18c). Apart the general pattern with HFS elements fractionated with respect to LIL elements, which is a general rule for the overall western Mediterranean ultrapotassic and associated rocks (e.g., Conticelli et al., 1986, 1997, 2002, 2004, 2007, 2009a), the Vico rocks show larger troughs at Ba, P, and Ti but smaller ones at Ta and Nb, with larger peaks at Pb than Classification and geochemical characteristics of the Vulsinian plagio-leucititic rocks. Other differences with Vico leucite-bearing ultrapotassic rocks and associ- Vulsinian rocks are observed in the normalized Th/U, Ta/ ated shoshonitic ones. A) Total Alkali-Silica (TAS) classification diagram (Le Maitre, 2002). B) K O wt.% Nb, Nd/Sr, Zr/Hf ratios (Fig. 18c). Fractionation of Th/U 2 vs. SiO2 wt.% classification diagram with reported the has been found to be a peculiar characteristic of the Vico grid for orogenic volcanic rock suites (Peccerillo & volcano with respect to the other Roman volcanoes (Vil- Taylor, 1976). C) Incompatible trace element patterns lemant & Palacin, 1987; Villemant & Fléhoc, 1989; for mafic volcanic rocks normalised to the primordial mantle values of Sun & McDonough (1989). Data from Avanzinelli et al., 2008). Barbieri et al. (1988); Perini et al. (1997, 2000, 2003, 2004).

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3. Sabatini district and ignimbrites; 11) Messinian-Pliocene post-orogen- The volcanic style of the Sabatini volcanoes was ic marine deposits; 12) Allochtonous Flysch. mainly explosive but lava flows are also abundant and All ages mentioned in the following discussion are vented from several different centers spread out over the 40Ar-39Ar ages, unless otherwise stated. Distal tephra lay- entire district area (Fig. 19; Conticelli et al., 1997). There ers probably related to the early Sabatini history, found in are three caldera depressions, which are from east to well cores, are dated between 0.8 and 0.76 Ma (Florindo west: Sacrofano, Baccano and Bracciano caldera (Fig. et al., 2007), followed by other pyroclastic deposits, al- 19; De Rita et al., 1983, 1988 1993a, 1993b; De Rita & ways in distal sections, that cover the time span from Zanetti, 1986; De Rita & Sposato, 1986). The Sabatini 0.65 Ma (Karner et al., 2001a) till the emplacement of district developed within the southeastern prosecution of Morlupo block and ash deposit (0.59 Ma, Cioni et al., the NW–SE Siena-Radicofani and Paglia-Tevere exten- 1993). Continuous volcanic activity, characterized by sional basin (e.g., Baldi et al., 1974; Locardi et al., 1976; large volumes of products, started at about 0.59 Ma and Barberi et al., 1994). Analogously to the Vico district al- lasted till about 0.4 Ma. The activity of the first period so the Sabatini overlap partially, on its western portion an continued in the eastern sector (Fig. 19) with the em- older volcanic complex belonging to the Tuscan Mag- placement of the “Tufo Giallo della Via Tiberina” ignim- matic Province, which is the Tolfa-Ceriti Dome Complex brite (0.55 Ma, Karner et al., 2001a), and then moved al- (Figs. 11, 19), made of leucite-free shoshonitic to high-K so to the western sector of the district where strong pa- calc-alkaline rocks belonging to the Pliocene lamproite- rossistic eruptions produced the “Prima Porta” ignim- shoshonite-calc-alkaline suite of the Tuscan Magmatic brite (0.51 Ma: Karner et al., 2001a), the “Grottarossa ” Province (Fig. 12b). These pre-Sabatini volcanic rocks pyroclastic sequence (0.52 Ma: Karner et al., 2001a), the outcrop within the volcanic cover of the Sabatini district “Tufo Terroso con Pomici Bianche” (0.49 Ma: Karner et at Manziana and Monte Calvario areas, and define the al., 2001a), the “Tufo Grigio Sabatino” (also called “Tufo southwestern and northwestern edges of the district (Fig. Rosso a Scorie Nere Sabatino”) a red tuff with black 19). On the basis of geological and volcanological re- pumice (0.43 Ma, K/Ar: Evernden & Curtis, 1965; 0.45 cords the volcanic activity of Sabatini district has been Ma: Cioni et al., 1993, Karner et al., 2001a), the “Peperi- divided in five different periods (e.g., Conticelli et al., ni Listati” ignimbrite (0.45 Ma: Cioni et al., 1993). The 1997; Karner et al., 2001a). third period of activity was mainly characterised by effu- Figure 19. Geological sketch map of the Sabatini district sive eruptions with lava flows alternated to large volume (Roman Magmatic Province). of fallout and surges deposits, the latter grouped in the “Tufi Varicolori della Storta” (0.41 Ma: Karner et al., 2001a), and the “Tufi Stratificati Varicolori di Sacrofa- no” pyroclastic sequences (Fig. 19). The activity of this period was concluded by the “Tufo Giallo di Sacrofano” ignimbrite (0.29 Ma: K/Ar, Fornaseri, 1985; 40Ar-39Ar, Karner et al., 2001a; Sottili et al., 2010). During this period both the Bracciano and Sacrofano calderas were formed (De Rita et al., 1983, 1993a). The fourth period of activity produced several monogenetic centers widely distributed over the entire district (Fig. 19). Most of them produced a single lava flow associated to scoria cones. The most intense monogenetic activity was concentrated in the Rocca Romana - Trevignano area, in the north- Geological sketch map of the Sabatini district. Leg- end: 1) Holocene alluvial and lacustrine deposits; 2) western sector, but cinder cones have been also found in travertine; 3) scoria cones; 4) phreatomagmatic de- the eastern sector as well (Monte Maggiore, Colle Aguz- posits from the final Sacrofano caldera phase and the zo, Casale Francalancia; Fig. 19), and at the border of the recent maars; 5) pozolanaceous ignimbrites; 6) fall deposits; 7) lithoidal ignimbrites; 8) undersaturated Bracciano caldera (Trevignano, Vigna di Valle). The fifth lavas; 9-10) Manziana-Ceriti rhyodacitic domes, lavas

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 34 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ period of activity concentrated in the central sector of the Figure 20. Classification and incompatible trace element district, in the area between the Bracciano and Sacrofano characteristics of Pleistocene volcanic rocks from Sabatini volcanoes. calderas (Fig. 19), with hydromagmatic activity that produced the tuff ring and tuff cones of Stracciacappe, Mar- tignano, and Baccano. Age data just out clarify the more recent activity of this volcanic district, with the hydromagmatic centres concentrated at about 0.1-0.09 Ma (Sottili et al., 2010); these ages confirm the previous youngest recorded age, 0.09 Ma (K/Ar, Fornaseri, 1985a). Apart the Morlupo trachyte, which represents a very small outcrop of hybrid products at the very beginning of activity, and the Vigna di Valle leucite-bearing latite, a Bracciano post caldera lava, the rest of the Sabatini volcanic rocks are made up exclusively by silica-undersaturated volcanic rocks (Cundari, 1979; Conticelli et al., 1997), ranging in composition from leucite-bearing tephrites to phonolites (Fig. 20a). Alkali and potassium lost (Fig. 20a,b) during syn-depositional transformation of leucite in analcite is observed in pyroclastic juvenile fragments of the Sabatini volcanoes (Parker, 1989). Cli- nopyroxene and leucite are the most abundant phenocryst phases with olivine restricted to the most evolved terms. Groundmasses are made up of leucite, clinopyroxene, plagioclase, nepheline, phlogopite, magnetite, and apatite. Titanite and haüyne have been found as accessory minerals in the most extreme differentiated phonolites (authors’ unpublished data). The Vigna di Valle lavas are the less silica undersaturated lavas, and beside the centi- metric leucite megacrysts/xenocrysts the rocks is made up of hyalophane and Barium-phlogopite crystals as well. Clinopyroxene are salitic in composition with strong zoning and abundant aluminium, enough to fill completely the tetrahedral site and to partition it in the octahedral (Cundari & Ferguson, 1982; Dal Negro et al., 1985; Cel- lai et al., 1994). Incompatible trace element contents of Sabatini vol- Classification and geochemical characteristics of the Sabatini leucite-bearing ultrapotassic rocks. A) Total canic rocks have similar distribution and fractionation to Alkali-Silica (TAS) classification diagram (Le Maitre, leucite-bearing rocks of other volcanoes of the Roman 2002). B) K2O wt.% vs. SiO2 wt.% classification dia- Province (Fig. 20c), with negative spikes at Ba, Ta, Nb, gram with reported the grid for orogenic volcanic rock P, Hf, and Ti, and peaks at Rb, Pb, Sr. Although mostly suites (Peccerillo & Taylor, 1976). C) Incompatible trace element patterns for mafic volcanic rocks nor- ultrapotassic rocks are observed in the Sabatini volcanic malised to the primordial mantle values of Sun & activity, a slight decrease in K2O and incompatible ele- McDonough (1989). Data from Conticelli et al. (1997). ment is observed passing from pre-caldera to post-calderas periods (Conticelli et al., 1997). The observed de- at the passage from pre- to post-caldera activity in the crease in the total amount of incompatible trace elements leucite-bearing series of Vulsinian volcanoes and Vico at the same level of differentiation has been already seen

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 35 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ ones. In the latter cases, however, beside these leucite- activity: a) external to the caldera rim, with the Santa bearing post-caldera series, leucite-free rocks have been Maria della Mole lavas, the Pantano-Borghese centers and the Monte Due Torri cones and lavas; b) caldera- erupted in the very last phases of volcanism. Indeed at rim monogenetic activity that occurred along the Latera volcano (Vulsinian district) and at Poggio Nibbio northern and western edges of the Caldera (Tuscola- (Vico district) leucite-free olivine-bearing shoshonitic no and Artemisio alignements); c) internal to the caldera, with the formation of the composite volcano of trachybasalts are observed as the last eruption of the vol- Monte delle Faete; III) The Via dei Laghi period, char- canic cycle in these two districts (Figs. 16 and 18). At the acterised by phreatomagmatic activity with little mag- Sabatini district none of these mildly alkaline composi- matic activity. tions have been observed, but it might not be excluded Legend: 1 & 2) alluvial deposits; 3) travertine; 4) Tavo- that magmas involved in the final hydromagmatic activi- lato formation; 5) Albano maar; 6) Nemi maar; 7) other ty of Baccano-Martignano-Stracciacappe might have a maars; 8) subplinian fall; 9) lower Faete succession; 10) upper Faete succession; 11) Tuscolano Artemisio shoshonitic affinity rather than ultrapotassic. (T.A.) scoria; 12) T.A. welded scoria; 13) T.A. lavas; 14 & 15) Pantano Borghese scoria & lavas; 16 & 17) San- Figure 21. Geological sketch map of the Colli Albani (Alban ta Maria delle Mole scoria & lava; 18 & 19) plateau Hills) district (Roman Magmatic Province). lavas & ignimbrites; 20) Sabatini volcanic products; 21 & 22) sedimentary sequences; 23) caldera rim; 24) cinder cones; 25) maars; 26) inferred caldera rim; 27) fault. Re-drawn after Giordano et al. (2006), and Boari et al. (2009a).

4. Alban Hills (Colli Albani) district The Colli Albani (Alban Hills) is a large flat stratovolcano with a central polygenetic caldera, and a dispersed post-caldera activity (Fig. 21). It was active from 0.6 Ma till recent times (e.g., Giordano et al., 2006, 2010; Marra et al., 2008, and references therein). It is located immediately south of Rome, some 15 km from the center of the city, on whose rocks the Ethernal city was built on and by (Funiciello et al., 2008). Volcanic activity occurred at the intersection of a NW-SE extensional basin, the Latin Valley, which represent the natural southward prosecution of the Siena-Radicofani-Paglia extensional basin, with a NE-SW and N-S systems of extensional and strike-slip faults (Faccenna et al., 1994a, 1994b, 1994c; De Rita et al., 1995). Volcanic rocks lie over Pliocene- Pleistocene marine sands and clays, and over the bordering horsts made of Triassic/Miocene platform carbonate units (Funiciello & Parotto, 1978; Danese & Mattei, 2010). According to Giordano et al. (2006, 2010), volcanic activity of the Colli Albani volcano can be divided into three main periods: i) the “Vulcano Laziale” period, ii) the “Tuscolano Artemisio – Monte delle Faete” period, and iii) the “Via dei Laghi” period (Fig. 21). Polygenetic Geological sketch map of Colli Albani volcano with reported the three main periods of activity: I) Vulcano caldera collapse is the main volcano-tectonic characteris- Laziale Period (pre-caldera), characterised by central tic delimiting the activity of the first period. The volume activity with predominant paroxysmal explosive erup- of the erupted volcanic rocks decreases greatly with time: tions and fissural lava flows; II) Tuscolano Artemisio – 3 3 Monte delle Faete period (post-caldera), characterised from some 300 km during the first period to ca. 1 km by the occurrence of six different sectors of volcanic

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 36 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ during the last period. The Vulcano Laziale volcanic edi- produced ca. 40 km3 of erupted products: i) the Monte fice cover an area of about 1,600 km2, with an ignimbrite delle Faete, which is a stratovolcano (944 m a.s.l.) built plateau associated with a piece-meal caldera complex, up in the middle of the caldera; ii) the Tuscolano Artemi- with over 300 km3 of dominantly pyroclastic products sio composite edifice, which is made of coalescent scoria and subordinate lava (Fornaseri et al., 1963; De Rita et cones and lava flows aligned along circum- and extra- al., 1995; Giordano et al., 2006, 2010). Early volcanic caldera fracture; iii) the Pantano Borghese monogentic activity generated the Pisolitic Tuffs succession (0.6-0.5 alignement, which is external to the caldera rims on the Ma; De Rita et al., 2002 and reference therein), which is NE sector of the district; iv) the Santa Maria della Mole interbedded with distal early pyroclastic from Sabatini monogenetic alignement, which is external to the caldera volcanoes (Karner et al., 2001a, 2001b; Marra et al., rims on the NW sector of the district; v) the Monte Due 2009). All ages mentioned in the following discussion are Torri-Ardea monogenetic alignment, which is made of an 40Ar-39Ar ages, unless otherwise stated. The largest volu- alignement of scoria cone across the caldera alon a NE- metric units are represented by the Pozzolane Tuffs suc- SW trending fracture. cession (0.46-0.35 Ma, Giordano et al., 2010 and referen- The most recent period of volcanic activity (i.e., “Via ces therein), a sequence of three large ignimbrites with dei Laghi” period) was concentrated on the south-western intermediate compositions (Fig. 23a). The "Pozzolane flank of the volcano (Giordano et al., 2006; Freda et al., Rosse" (0.457 Ma, Karner et al., 2001a), the "Pozzolane 2006) with prevalent but small phreatomagmatic erup- Nere" (0.407 Ma, Karner et al., 2001a; 0.405±0.003 Ma, tions (Fig. 21), for the interaction with shallow produc- K/Ar, Karner et al., 2001c) and the "Tufo Lionato-Pozzo- tive aquifers (e.g., De Benedetti et al., 2008). The phrea- lanelle" are the main ignimbrites (Watkins et al., 2002; tomagmatic activity brought about the disruption of the Giordano et al., 2006, 2010). The "Tufo Lionato-Pozzola- SW rim of the caldera, with the formation of several coa- nelle" forms the "Villa Senni" Formation, related to the lescent maars aligned along both NNW-SSE and NS re- last caldera collapse of the Colli Albani volcano, and regional trends (e.g., de Rita et al., 1988, 1995; Funiciello sponsible for the present day configuration of the caldera. et al., 2003). The temporal extent of the last activity of Several ages are present in literature for the "Tufo Liona- the Alban Hills has been matter of debate for years and to" (0.355 Ma, Karner et al., 2001a; 0.365 Ma, Marra et involved U/Th and 40Ar-39Ar datings: an experiment per- al., 2009) and "Pozzolanelle" [0.35±0.03 Ma, average of formed with the two methods on the same samples gave 3 Rb/Sr isochron ages, and 0.34 (0.35 Ma updating the on average discordant ages, being U/Th data below ~ age of the used monitor) ±0.007 Ma, average of 7 0.025 Ma, noticeably younger than 40Ar-39Ar data (Villa, 40Ar-39Ar ages on leucites, Radicati et al., 1981; 0.357 1992; Voltaggio et al., 1994). The polygenetic Albano Ma, Karner et al., 2001a]. Indeed, today the caldera has maar is the last formed and produced phreatic activity an 8 km diameter and it is asymmetric with a horse-sha- since about 0.07 Ma (Marra et al., 2003; Freda et al., ped wall. Between major caldera forming eruptions vol- 2006; Giaccio et al., 2009). The end of the Albano activi- canic activity was intra-caldera and localised along peri/ ty is debated too: Freda et al. (2006) and Giaccio et al. extra-caldera fissures: the Vallerano lavas (0.46 Ma, Ber- (2009) established the last volcanic episode at ~0.04 and nardi et al., 1982, K/Ar; Karner et al., 2001a, 40Ar-39Ar), ~0.03 Ma, respectively, while other authors extend the Corcolle and Fontana Centogocce units, which, are domi- activity throughout the Holocene (Villa et al., 1999; Fu- nantly made up of tephra fall units and lava flows. niciello et al., 2003; De Benedetti et al., 2008). With the formation of the caldera in its present day The most stricking feature of the Colli Albani rocks is morphology, the volcano changed drastically its volcanic their more silica-undersaturated character with respect to style and feeding system, with arrival to the surface of the other leucitites and plagio-leucitites of the Roman magmas through several different pathways. Lavas of the Province (Fig. 22a, 22b), which is accompayned by high- post caldera period have been dated between 0.35 and er MgO and CaO contents of volcanic rocks (Tables 4 0.15 Ma (K/Ar, Bernardi et al. 1982; 40Ar-39Ar, Karner and 5). Also the four main ignimbrites have chemical et al. 2001a, Marra et al. 2003). Five main sectors of compositions of the juvenile fragments, representing the post-caldera vocanic activity have been recognized composition of the magma triggering the eruption, never (Giordano et al. 2006, 2010 and Boari et al., 2009a) and exceeding tephritic-phonolite compositions, but with

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Figure 22. Classification and incompatible trace element some ignimbrites (i.e., Pozzolane Rosse, and Pozzola- characteristics of Pleistocene volcanic rocks from Colli nelle) with phonolitic tephritic and tephritic compositions Albani volcano. as well (Figs. 22a, 22b). This is the major compositional difference with other Latium volcanoes, where ignimbrites have invariably a phonolitic to trachyphonolitic compositions (Figs. 16a, 18a, 20a). This has been thought to represent a problem for the passive enrichment of vol- atites needed to trigger parossistic eruptions, and for this reason Freda et al. (1997) claimed for a supply of CO2 to early trigger eruptions from carbonate syntexis. This process has been widely discussed by several authors who found in some specific cases the evidence to support it, but in other cases questioned the abuse of this differentiation process (e.g., Freda et al., 2007; Iacono Marziano et al., 2007, 2008; Boari et al., 2009a; Gaeta et al., 2009; Conticelli et al., 2010; Peccerillo et al. 2010). These compositional differences indicate that Colli Albani magmas have lower silica activity and alumina saturation than other Roman magmas, such to stabilize melilite in many silica undersaturated volcanic rocks, to prevent crystallization of either plagioclase or K-feldspar (Conti- celli et al., 2010). Among phenocrysts, Leucite is among the most abundant mineral in pre-caldera pyroclastic rocks, and in the Monte delle Faete lavas and pyroclastic rocks, whereas is confined in the groundmasses of Pre- caldera plateau melilititic lavas, and post-caldera ones. Clinopyroxene is a ubiquitous phenocryst mineral, often showing complex zoning (Aurisicchio et al., 1988; Gaeta et al., 2005). Olivine is confined in the most mafic pre- and post-caldera lavas, and like in all other ultrapotassic volcanoes it has euhedral chromite inclusions. In the groundmasses beside minerals found as phenocrysts, Ba- phlogopite, Ti-magnetite, nepheline, Ca-Fe olivines and apatite are also found (e.g., Gaeta et al., 2000; Conticelli et al., 2010; Melluso et al., 2010). Akermanitic melilite crystals are confined to the groundmasses of most silica- Classification and geochemical characteristics of the undersaturated foidites of the pre- and post-caldera peri- Colli Albani volcanic rocks. A) Total Alkali-Silica (TAS) ods. The Capo di Bove (e.g., Cecilite, Washington, 1906) classification diagram (Le Maitre, 2002). B) K2O wt.% vs. SiO2 wt.% classification diagram with reported the and the Osa foidites are the best examples among post- grid for orogenic volcanic rock suites (Peccerillo & caldera lavas. Melanite garnet, gehlenitic melilite and Al- Taylor, 1976). C) Incompatible trace element patterns spinel are typical minerals of skarn ejecta (Federico & for mafic volcanic rocks normalised to the primordial mantle values of Sun & McDonough (1989). Data from Peccerillo, 2002), and they are found as xenocrysts in py- Fornaseri & Scherillo (1963); Laurenzi (1980); Pecceril- roclastic rocks of the Via dei Laghi hydromagmatic ac- lo et al. (1984); Ferrara et al. (1985); Francalanci et al. tivity (Conticelli et al., 2010). (1987); Trigila et al. (1995); Freda et al. (1997); Palladi- no et al. (2001); Conticelli et al. (2002, 2007, 2010); The primordial mantle normalized patterns (Figs. 22c) Freda et al. (2006); Gaeta et al. (2006); Giordano et al. show significant differences between mafic MgO-rich (2006); De Benedetti et al. (2008); Boari et al. (2009a). magmas from pre- to post-caldera. Indeed, pre-caldera

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 38 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ leucititic and melilititic magmas show smaller throughs rocks of this district; a name that better defines the out- at Ba, and Hf, with respect to post-caldera ones. In addi- crop locality and the geographic area than Hernican, the tions differences in LIL elements total abundances are al- original name choosen for this volcanic field and kept for so observed (Figs. 22c). Boari et al. (2009a) explained several years in the Earth Science literature. this characteristic as due to a different supply of magma The volcanism of the Middle Latin Valley district de- from a slightly different mantle source. Pre-caldera mag- veloped during the Pleistocene (Basilone & Civetta, mas should have been produced by smaller degrees of 1975; Fornaseri, 1985a; Boari et al., 2009b). Among the partial melting, at higher pressure, of a veined metasoma- Roman districts the Middle Latin Valley is the only one tised upper mantle than post-caldera parental magma. that lacks a large volcanic edifice; only small volumes of primitive magmas erupted from small scattered volcanic Figure 23. Geological sketch map of the Middle Latin Valley centers (Civetta et al., 1979, 1981; Pasquaré et al., 1985; district (Roman Magmatic Province). Boari, 2005; Boari & Conticelli, 2007; Frezzotti et al., 2007; Boari et al., 2009b; Nikokossian & van Bergen, 2010). The total volume of erupted magma is significantly lower than that observed in all the other volcanic districts of the Roman Magmatic Province, probably due to the distinctive geological and geodynamic evolution of the Apennine chain and Adriatic foreland in this area. The volcanic field is clustered in a narrow area well within the Sacco River valley, the median sector of the Latin Valley, located between the Apennine chain and the Monti Lepini (Fig. 11). The Latin Valley is a NNW-SSE extensional basin. The volcanic field is made up of cinder cones, small lava plateau, short lava flows, and tuff rings with associated small volume of hydromagmatic pyroclastic flows (Patrica pyroclastic flows, Fig. 23). The vents are arranged along the NNW-SSE fault at the foot of Monti Lepini, which delimited the southwestern edge of the Latin Valley, and the N-S and NNE-SSW dextral strike-slip faults (Sani et al., 2004) (Fig. 23), both tectonic systems provided preferential pathways for the mafic Geological sketch map of the Middle Latin District. Redrawn after Pasquaré et al. (1985), Sani et al. low viscosity magmas uprise (Acocella et al., 1996). (2004), Boari & Conticelli (2007), Boari et al. (2009b). The absence of a large central volcanic edifice and of Main monogenetic volcanoes are represented by cin- a large area covered by pyroclastic deposits, which might der cones, tuff rings and small plateau-like lava flows. be used as stratigraphic markers, makes it difficult to re- 5. Middle Latin Valley district construct a reliable stratigraphic succession. Therefore The Middle Latin Valley district is located in the the volcanic history of the Middle Latin Valley volcanic Southern Latium area (Fig. 11), some 100 km south of fields has been reconstructed using geochronologic data Rome, and some 60 km from Ernici Mounts, the locality on each single volcanic center (Basilone & Civetta, 1975; to which this volcanism refers to with the name of Herni- Cortesi C. reported as personal communication in Forna- can District in the early scientific literature (Branco, seri, 1985a; Boari et al., 2009b). In addition, because the 1877; Viola, 1899, 1902; Washington, 1906). Being the grouping has been made on the basis of geochemical and volcanic field developed well within the Latin Valley, in petrological informations, the time succession is strongly its middle sector, several authors (e.g., Angelucci et al., integrated with compositional characteristics change 1974; Dolfi, 1981; Acocella et al., 1996; Boari, 2005; (Boari et al., 2009b). Boari & Conticelli, 2007; Frezzotti et al., 2007) used that the name “Middle Latin Valley” to refer the volcanic

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 39 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/

Figure 24. Classification and incompatible trace element Kamafugites are the early magmatic rocks to appear characteristics of Pleistocene volcanic rocks from Middle on surface in the volcanic field (0.7-0.6 Ma; Basilone & Latin Valley monogenetic volcanoes. Civetta, 1975; Boari et al., 2009b); they are represented by leucite-bearing melilitites with a paragenesis made of melilite, olivine, clinopyroxene, phlogopite, Ti-magnetite, nepheline and apatite; secondary calcite is also found to fill vesicles and fractures. The Patrica hydromagmatic tuffs have neither juvenile fragments nor glass shards as large as to perform whole rock or EPM analyses, respectively, thus their evolved kamafugitic nature was established on the basis of mineral compositional data on loose crystal fragments (Boari & Conticelli, 2007). Patri- ca pyroclastic units display a much younger 40Ar-39Ar age, ~0.42 Ma (Boari et al., 2009b), which matches the K/Ar value of 0.4 Ma given by Fornaseri (1985a). All ages mentioned since now in the following discussion are 40Ar-39Ar ages, unless otherwise stated. Leucitites appears as early as kamafugites at Piglione center at about 0.61 Ma (Boari et al., 2009b). Plagioclase leucitites appears slightly later (Giuliano di Roma, and Tecchiena), between 0.41 and 0.39 Ma (Boari et al., 2009b), although a younger age of 0.25 Ma has been found for the Colle Sant’Arcangelo leucitite (Boari et al., 2009b). The leucitites and plagio-leucitites are mostly phonolitic tephrites (Fig. 24a), with no or limited differentiation (Figs. 24a, 24b). Few tephrites are also found at Selva dei Muli cinder cone and Pofi volcano. Mineralogy of leucitites and plagio-leucitites is made preferentially by leucite + clinopyroxene ± olivine ± plagioclase ± Ti-magnetite ± apatite ± phlogopite. Monogenetic volcanoes that produced leucitites and plagioclase leucitites are generally located along the N-S and NNE-SSW dextral strike-slip faults (Fig. 23). Volcanic rocks with shoshonitic affinity (Fig. 24b) appear as late as 0.36 and 0.35 Ma (Boari et al., 2009b). These volcanic rocks have trachy-basaltic compositions (Fig. 25a) with phenocrysts of olivine and clinopyroxene, set in a groundmass made of clinopyroxene, olivine, plagioclase, and Ti-magnetite; in some samples leucite crystals are also found in the groundmass (Boari Classification and geochemical characteristics of the Middle Latin Valley volcanic rocks. A) Total Alkali-Sili- & Conticelli, 2007). Basalts with calc-alkaline affinity ca (TAS) classification diagram (Le Maitre, 2002). B) (Boari, 2005; Boari & Conticelli, 2007; Frezzotti et al., K2O wt.% vs. SiO2 wt.% classification diagram with 2007) have been vented from the same centers of sosho- reported the grid for orogenic volcanic rock suites nitic products at Colle Spinazzeta, Selva Piana, and La (Peccerillo & Taylor, 1976). C) Incompatible trace element patterns for mafic volcanic rocks normalised to Badia, where basalts are stratigraphically younger than the primordial mantle values of Sun & McDonough shoshonitic ones. Basaltic scoriae from the Pofi scoria (1989). Data from Boari et al. (2009b). cone has given an age of 0.29 Ma (Boari et al., 2009b), which disagrees with the K/Ar ages on the underlying

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 40 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ lava flows of the plateau, 0.11 and 0.08 Ma (Fornaseri, also the highest abundance in incompatible trace ele- 1985a). The leucititic lavas that gave these very young K/ ments, and the normalized incompatible trace element Ar ages show stratigraphic correlation with the lavas of patterns recall closely those of pre-caldera melilitites and the Pofi plateau (Angelucci & Negretti, 1963), dated at leucitites of the Colli Albani district (Fig. 22c), with pe- 0.40 Ma, (K/Ar, Basilone & Civetta, 1975). A basaltic culiar smaller negative spikes at Ba, and larger at Ta, Nb, lava from Colle Vescovo, a final center in the Selva Pia- P, and Zr with respect to younger magmas (Fig. 24c). na area, gave an age of 0.3 Ma (Boari et al., 2009b), co- Passing from kamafugite to leucitite/plagio-leucitite maf- herent with the scoria sample of Pofi. These calcalkaline- ic rocks with time, it is observed also an increase of the like basalts (Fig. 24a) have significantly lower K2O than negative spikes at Ba, Sr and P, which is coupled to a de- any other Middle Latin Valley rocks, overlapping partial- crease of the troughs at Ta, Nb, and Ti (Fig. 24c). This ly with altered shoshonites where K2O has been removed trend is continuous with time passing also from leucitites by secondary processes (Fig. 24b). These altered rocks to shoshonite and calc-alkaline mafic rocks. In addition, are also characterized by secondary minerals and weath- it is worthy to note the normalized Ta/Nb ratio that pass ering textures (Boari, 2005; Boari & Conticelli, 2007). from a value <<1 in kamafugites to values > 1 in the Basalts with calc-alkaline affinity are characterized by youngest volcanic rocks (i.e., calc-alkaline; Fig. 24c). sub-porphyritic textures with olivine and clinopyroxene phenocrysts with groundmass made of plagioclase + Figure 25. Geological sketch map of the Roccamonfina glass + clinopyroxene Ti-magnetite + olivine (Boari, district (Roman Magmatic Province). 2005; Boari & Conticelli, 2007; Boari et al., 2009b). Monogenetic volcanoes and centres that vented lavas with shoshonitic and calc-alkalic petrologic affinities are generally located along the NNW-SSE normal fault delimiting the Monti Lepini-Monti Ausoni ridge (Fig. 23). The lack of a large volcanic apparatus and therefore of a structured system of magma chambers beneath the Middle Latin Valley volcanic field is probably the reason for missing magmatic differentiation at shallow depth, and therefore for outcropping of mafic primitive igneous compositions (Tables 4, 5, and 6). This characteristics permit to observe a large compositional spectrum in terms of silica and K2O contents (Fig. 24b) that might be present also in the other volcanoes of the Roman province, hidden by shallow level differentiation and compositional buffering of the different magmas produced with time in the mantle source. This permits also to observe Geological sketch map of the Roccamonfina volcano the variation of trace element contents with time and po- (redrawn after: Giannetti, 1964, 2001; Taylor et al., tassium contents of primitive MgO-rich magmas (Fig. 1979; Cole et al., 1992; Giordano et al., 1998a, 1998b; Conticelli et al., 2009b). Legend. 1 - Campanian Ig- 24c). Indeed as already shown for other magmatic prov- nimbrite (erupted from Campi Flegrei); 2-5 Late phase inces of the Mediterranean region it is possible to argue a of post-caldera activity (Vezzara synthem; 155-50 ka); direct and positive correlation between incompatible 2 – HKCA final lavas; 3 – Shoshonitic mafic lava and pyroclastics from monogenetic centers; 4 – Shosho- trace element contents and potassium enrichment in maf- nitic domes; 5 – Yellow Trachytic Tuff; 6-8 - Early ic primitive MgO-rich volcanic rocks (Conticelli et al., phase of post-caldera activity (Riardo synthem; 2009a). The same holds true for the Italian ultrapotassic 385-230 ka); 6 – White Trachytic Tuffs; 7 – Teano pyroclastic succession; 8 – Brown Leucitic Tuff; 9 – Pre- volcanic rocks, from Western Alps (Fig. 8) to Corsica caldera activity Leucite-bearing lava and pyroclastics (Fig. 10), Tuscany (Fig. 12), and Roman Province (Figs. (HKS) (Roccamonfina synthem; 630-385 ka); 10 – Mesozoic-Cenozoic pre-orogenic carbonatic-terrige- 16, 18, 20, and 22). Indeed, the most K2O enriched mafic rocks of the Middle Latin Valley (i.e., kamafugites), have nous succession; 11 – Main extensional faults; 12 – caldera rim; 13 – scoria cones.

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 41 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/

6. Roccamonfina district volcano-tectonic depression (Cole et al., 1992a; De Rita The volcano of Roccamonfina is stratovolcano char- & Giordano, 1996; Giannetti, 2001). acterized by sector collapses and an apical central caldera (Fig. 25) (Cole et al., 1992; De Rita & Giordano, 1996; Figure 26. Classification and incompatible trace element characteristics of Pleistocene volcanic rocks from Giannetti, 2001; Rouchon et al., 2008). It belongs to the Roccamonfina volcano. Roman Magmatic Province (Washington, 1906; Avanzi- nelli et al., 2009). It was the first volcano in which a “low potassium series” accompanying leucite-bearing ultrapotassic rocks was recognized (Appleton, 1972). The Roccamonfina volcano is located at the intersection of a NNW-SSE extensional basin with important NE-SW and N-S tectonic lineaments, which cut the Mes- ozoic-Cainozoic Apennine carbonatic sequences (Accor- di, 1963; Incoronato et al., 1985; Accordi & Carbone, 1988; Mattei et al., 1995; Giordano et al., 1995; Bosi & Giordano, 1997). The volcanic succession lies on trans- gressive marine sedimentary sequence that filled the NE- SW Garigliano Graben (Ippolito et al., 1973; Watts, 1987; Giordano et al. 1995). The Roccamonfina volcano is made up by lavas and pyroclastic rocks erupted in three main periods of activity (Ballini et al., 1989a; De Rita & Giordano 1996; Giannetti, 2001; Rouchon et al., 2008). The beginning of the volcanic activity relies on the dating of the oldest products found in the well Gallo 85-1, above the sedimentary substratum: whereas K/Ar ages of the deepest lava are slightly discordant, the 40Ar-39Ar age on a lava sample lying ~50 m above the bottom of the volcanic pile gives 0.59 Ma, (Ballini et al., 1989a). All ages older than about 0.6 Ma present in literature are likely biased at some extent (Gasparini & Adams, 1969; Cortini et al., 1973; Giannetti et al., 1979; Radicati et al., 1988). The first period of activity was dominated by leucite-bearing lava flows interbedded to mi- nor ash fall and mud-flow deposits (San Carlo lavas), pe- ripheral dikes, parasitic monogenetic centres, and eccentric domes on the flank of the volcano were also emplaced (Di Girolamo et al. 1991). The volcanic rocks emitted during this period have leucititic to plagioclase- leucititic affinity, ranging form basanite to phonolite (Fig. 26a), and with a mineralogy made up of olivine, clinopyroxene, leucite, plagioclase, Ba-phlogopite, apatite, Classification and geochemical characteristics of the Ti-magnetite and amphibole, with sanidine and rare soda- Roccamonfina volcanic rocks. A) Total Alkali-Silica lite. A first stratocone destroying event occurred at 0.44 (TAS) classification diagram (Le Maitre, 2002). B) K2O wt.% vs. SiO2 wt.% classification diagram with repor- Ma with the formation of a lateral sector collapse (Rou- ted the grid for orogenic volcanic rock suites (Pecce- chon et al., 2008), but leucite-bearing volcanic activity rillo & Taylor, 1976). C) Incompatible trace element did not interrupt and continue with the building up of a patterns for mafic volcanic rocks normalised to the new stratocone, which covered almost completely the old primordial mantle values of Sun & McDonough (1989). Data from Ghiara et al. (1973) Ghiara & Lirer (1977),

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Hawkesworth & Vollmer (1979), Vollmer & Hawkes- rim and external to the caldera range between 0.33 Ma worth (1981), Rogers et al. (1985); Giannetti & Luhr (Casale Robetti; 40Ar-39Ar; Laurenzi’s unpublished data) (1983), Luhr & Giannetti (1987), Conticelli & Peccerillo (1992); Giannetti & Ellam (1994); Conticelli et al. (2002, and 0.27 Ma (Colle Friello; K/Ar, Rouchon et al., 2008). 2007, 2009b), Rouchon et al. (2008). Post caldera volcanic rocks are leucite-free, and mostly belonging to the shoshonitic series (Fig. 26b). The The beginning of the formation of the summit caldera youngest leucite-free lava flows, which have been vented marked the passage to the second period of activity (De from a fracture on a flank of Monte Santa Croce dome, Rita & Giordano, 1996), which was characterised by pli- have revealed compositional variations pointing to the nian activity, with the eruption of five main, caldera HK-calc-alkaline field (Fig. 26b). forming pyroclastic flow units (Giannetti & Luhr, 1983; Beccaluva et al. (1991) pointed out that ultrapotassic Luhr & Giannetti, 1987; Ballini et al., 1989b; Cole et al., rocks outcropping below the 41st parallel display clear 1993; Giannetti, 1996; Giordano 1998a, 1998b; Giannetti difference in trace element distribution with respect to & De Casa, 2000), which are namely the Brown Leucitic those from above this parallel (Tables 5 and 6). The Roc- Tuff and the succession of the White Trachytic Tuffs camonfina volcano, is just few degree north from the 41st (Cole et al., 1992, 1993; De Rita et al., 1998; Giannetti & parallel and then ultrapotassic leucite-bearing rocks have De Casa, 2000). Pyroclastic units have a variable compo- incompatible trace element distribution similar to the oth- sition from phonolitic to trachytic. Recent K/Ar and er Latian districts. On the other hand, the post-caldera 40 39 Ar- Ar ages of the Brown Leucitic Tuff agree at 0.35 shoshonitic rocks from Roccamonfina have significantly Ma (Rouchon et al., 2008; Scaillet et al., 2008). The lower LIL elements with respect to any other Roman White Trachytic Tuff succession is stratigraphically rocks, and in particular with the other post-caldera shosh- much more complicated. Giannetti & De Casa (2000) onites of the northernmost Latian districts (Fig. 16c). present a range of ages comprised between 0.31 Ma for Shoshonitic rocks from the nearby Middle Latin Valley the lower unit till 0.23 Ma for the upper one. Laurenzi et district (Fig. 24c) display significant differences with real. (1990) suggested an interval between 0.32 Ma and spect to shoshonitic rocks from Roccamonfina both in <0.28 Ma for the whole serie, whereas Quidelleur et al. terms of total enrichments and of fractionation of HFS (1997) present an age of 0.33 Ma for the Lower Unit of with respect to LIL elements (Fig. 26c). With this re- the White Trachytic Tuff. The largest compositional spect, the Roccamonfina post-caldera shoshonites display range is observed among the juvenile clasts of the Brown trace element distribution similarities with volcanic rocks Leucitic Tuff, which is thought to be made by a single from the Neapolitan district (Tables 6 and 7) and at a cer- eruption, and thus that variability might be interpreted as tain scale with those from Lucanian Magmatic Province well as due to syn-depositional alkali-loss due to leucite (Conticelli et al., 2009b). As a corollary the leucite-bear- and glass transformation (Giannetti & Masi, 1989; Park- ing pre-caldera ultrapotassic rocks have no significant er, 1989). The White Trachytic Tuff falls well within the compositional differences with other Roman volcanic trachytic field (Fig. 26a). rocks from either Latium or Umbria regions. In summa- The third and last period of post-caldera activity was ry, the leucite-bearing ultrapotassic volcanism of Rocca- characterized by dome to monogenetic volcanism within monfina is well within the chronological, mineralogical the caldera, along the caldera edge, and on the flanks of and compositional limits of the Latian districts of the Ro- the primordial Roccamonfina volcano (Fig. 25). The geo- man Magmatic Province. chronological data on the rocks of this period do not per- 7. Umbrian District mit to define exatly the last lava flow eruption which is Washington (1906) fails to describe the ultrapotassic vented from a fracture on the western flank of Monte rocks found in the intra-apennine area. The monogenetic Santa Croce Dome and flowed down the miffle of the volcano of San Venanzo and the lava center of Cupaello caldera at the foot of Monte Lattani intra-caldera dome. are the major volcanic outcrops of the Umbria districts Indeed the Monte Santa Croce dome yielded the young- (Rodolico, 1937; Mittempergher 1965; Sartori, 1965) and est ages found at Roccamonfina (K/Ar, 0.16 Ma, Radicati they were already known in the Italian scientific litera- et al., 1988; 0.15 Ma, Rouchon et al., 2008). Samples ture since the end of the XIXth century (Verri, 1880; Sa- from cinder, scoria cones and lava flows on the caldera batini, 1899). Several other sites in intra-apenninic areas

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 43 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ with occurrence of volcanic rocks have been reported re- Reatini at the edge of the Rieti extensional basin (Cavina- cently (e.g., Accordi & Angelucci, 1962; Durazzo et al., to et al., 1989; Zanon, 2005). 1984; Bellotti et al., 1987; Stoppa, 1988; Michetti & Ser- va, 1991; Traversa et al., 1991; Brunamonte et al., 1992; Figure 27. Geological sketch map of the San Venanzo volcanic field (Roman Magmatic Province). Stoppa & Lavecchia, 1992; Cipollari et al., 1998; Tallini et al., 2002). In some cases these outcrops are just an- cient volcanoclastic levels (e.g., Peglio and Petrasecca; Cipollari et al., 1998), in other cases are levels of airfall tuffs from either the main Roman volcanoes or Etna (Sa- batini, Colli Albani, Neapolitan volcanoes, Mirco, 1990; Tallini et al., 2002; Wulf et al., 2004), and eventually they are pyrometamorphic rocks originate either by carchoal pit burning or by natural coal combustion (e.g., Melluso et al., 2003, 2005a, b; Capitanio et al., 2004; Grapes, 2006). Only for Monte Autore, La Queglia, and Polino outcrops the magmatic and the provenance nature have not been questioned. In the first case, the strong alteration allows the obtaining neither of a petrographic de- scription nor of a bulk chemical analysis; based on clinopyroxene composition the Roman nature of the Monte authore dyke was inferred (Mirco, 1990). The La Queglia dyke is a typical alkaline lamprophyre intruded in a carbonate platform during the Eocene, much earlier than orogenic processes involved this unit in the Apennine chain (Durazzo et al., 1982; Mirco, 1990). The Polino rock has a clear alvikitic bulk composition although a hot debate within the scienfic literature questioned its primary mantle nature versus carbonate contamination with surrounding limestones (e.g., Stoppa & Lupini, 1993; Peccerillo, 1998, 2004, 2005b; D’Orazio et al., 2008). In the lights of the strong diversity on emplacement Geological sketch map of the San Venanzo volcanic field (Umbria district). Legend: 1) Miocene sandstones mechanisms, nature and genesis of the rocks found with- and marly flysh of the Umbrian sedimentary se- in the Apennine chain we focus and limit our attention quence; 2) Plio-Pleistocene clay and sand; 3) San only on the classical outcrops that present a wide consen- Venanzo maar – breccia flow deposit; 4) Pian di Celle tuff cone – pyroclastic deposits; 5) kalisilite-bearing sus about their ultimate magmatic nature and local vent- olivine melilitoite; 6) pyroclastic fall deposits of the ing: the San Venanzo, Cupaello, and Polino centers. San Venanzo and Celli volcanic centers; 7) volcanic San Venanzo and Cupaello monogenetic volcanic centers. Redrawn after Stoppa (1996) and Zanon (2004). centers (Fig. 11) are the only ones in which compositional features of volcanic rocks are unaltered and testify the The San Venanzo volcanic field includes three distinct original characteristics of ultrapotassic magmatism (Gal- eruptive vents: the San Venanzo maar, the Pian di Celle lo et al., 1984; Taylor et al., 1984; Peccerillo et al., 1988; tuff ring, and the Celli tuff cone (Fig. 27). A K/Ar age of Conticelli, 1989; Stoppa & Cundari, 1995; Stoppa, 1996; 0.46 Ma on leucite separated from a pegmatoid facies Zanon, 2005). They are located within the Apennine oro- was provided by Laurenzi & Villa (1984). After, a more genic chain. The San Venanzo lies on a horst bordering detailed chronological study gave a much younger the western sector of the Tiber River Valley extensional 40Ar-39Ar age of 0.27 Ma for a sanidine from the basal basin, whereas the Cupaello lava vented from a NW-SE tephra (Pian di Celle) (Laurenzi et al., 1994). Both phlo- normal fault bordering the southeastern foot of the Monti gopite and leucite of the pegmatoid veinlets showed

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 44 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ saddle-shaped age spectra, which account for the differ- for mafic volcanic rocks normalised to the primordial ence between K/Ar and Ar-Ar ages (Laurenzi et al., mantle values of Sun & McDonough (1989). Data from Peccerillo et al. (1988); Conticelli (1989), Conticelli & 1994). Peccerillo (1992); Conticelli et al. (2002, 2007).

Figure 28. Classification and incompatible trace element The Cupaello is a small lava tongue that has flowed characteristics of Pleistocene volcanic rocks from Umbrian down for few hundred meters above the lacustrine depos- monogenetic volcanoes. its of the Rieti valley (Rodolico, 1937; Gragnani, 1972; Cavinato et al., 1989; Stoppa & Cundari, 1995). For the Cupaello lavas, a kalsilite-enriched separate gave a saddle shaped spectrum with the only indication of a maximum age of ~ 0.64 Ma (Villa et al., 1991). The Polino outcrop is a narrow plug, some two meters in diameter, embedded in a heavy limestone sequence (ca. 6,000 meters; Michetti, 1990). Two 40Ar-39Ar ages are available for the Polino outcrop: ~ 0.4 Ma on sanidine from pyroclastic deposits and of 0.28 Ma on a massive block (Lau- renzi et al., 1994). The three outcrops of melilitites are characterized by different mineralogical assemblages of the relatively restricted whole rock compositional range (Table 4). In- deed all the samples from Umbria fall in the foiditic field (Fig. 28a) if exception is made for some Cupaello samples in which the weathering have decreased the total K2O with consequent slight increase of SiO2 (Fig. 28a, 28b). On the other hand, the samples from Polino rock do not fall within the range of the diagrams of figures 28a and 28b, but it has consistently lower silica, K2O and Na2O (Table 4) to claim for a possible carbonatitic nature (Stoppa & Lupini, 1993; Stoppa & Woolley, 1997; D’Or- azio et al., 2008; Stoppa et al., 2008). On the basis of major element chemistry and mineralogy the Umbrian rocks belongs to the kamafugitic clan (Table 1). Åkermatite-rich melilite is the most characteristic mineral of Umbrian rocks (Fig. 3), which reflects the very low silica activity, which is a consequence of the strong silica-undersaturation of the magma. Melilite- bearing rocks display the lowest silica and the highest CaO among volcanic rocks such to determine the appearance of larnite in their CIPW norm. Melilite coexists with a limited number of common minerals and appears to be equally stable with K-rich and Na-rich minerals. In igneous rocks melilite has never been found in equilibrium with either plagioclase or K-feldspar (Yoder, 1972). In Classification and geochemical characteristics of the the Umbrian rocks melilite is found in equilibrium with Umbrian kamafugitic rocks. A) Total Alkali-Silica (TAS) classification diagram (Le Maitre, 2002). B) K2O wt.% feldspatoids, both leucite and kalsilite. In the San Venan- vs. SiO2 wt.% classification diagram with reported the zo rocks large phenocrysts of olivine are found, whereas grid for orogenic volcanic rock suites (Peccerillo & clinopyroxene is restricted to the groundmass together Taylor, 1976). C) Incompatible trace element patterns

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 45 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ with melilite, phlogopite, kalsilite, magnetite, and nephe- of the 41st parallel, and it is formed by four main volcan- line, with accessory perovskite, apatite, chromite, and ic apparata: the Ischia, Procida, Campi Flegrei and Som- monticellite (Conticelli, 1989; Cundari & Ferguson, ma-Vesuvius (Fig. 29). Most of the Neapolitan district 1992). On the other hand, in the Cupaello melilitites, oli- volcanoes developed during the Upper Pleistocene but vine is replaced by monticellite within the groundmass, with an intense volcanic activity piercing the Pleistocene- which is found in equilibrium with melilite, clinopyrox- Holocene boundary (Brocchini et al., 2001; De Vivo et ene, phlogopite, and kalsilite. Clinopyroxene and phlogo- al., 2001; Deino et al., 2004), and important historical pite are present as large phenocrysts. The Polino rock is eruptions recorded (e.g., Ischia, Campi Flegrei, Vesuvius; far from being an exhaustive and clear carbonatite. In- e.g., Santacroce, 1987; Rosi & Sbrana, 1987; Vezzoli, deed, phlogopite and olivine are the only phenocrysts 1987). A wealth of data regarding the recent phases of phases, and the groundmass is made of melilite, clinopyr- activity of these volcanoes is available, but we know lit- oxene, phlogopite, kalsilite, perowskite and monticellite. tle about the Middle Pleistocene history of Neapolitan Calcite is also found but its primary nature is still strong- volcanoes, because most of them buried by Holocene ly debated (Lupini & Stoppa, 1993; Barker, 1996; Pecce- volcanic activity, or just beneath the sea level. It is clear rillo, 1998; Wolley et al., 2005; Peccerillo, 2005b; D’Or- that shoshonitic volcanic products dominate over leucite- azio et al., 2008). bearing ultrapotassic rocks. In addition, in most of the Incompatible trace element concentration is among Neapolitan volcanoes, the silica-undersaturated ultrapo- the highest total abundances observed in Roman rocks. tassic rocks are completely missing in the geological re- The same distribution of other Mediterranean ultrapotas- cords, with the exception of Mt. Vesuvius, where they sic rocks is observed for normalised patterns with high appears lately, after a long period characerized by either field strength element, but not Th, fractionated with re- leucite-free or –poor volcanic rocks (e.g., Peccerillo, spect to large ion lithophile elements, a characteristic typ- 2005a; Avanzinelli et al., 2009, and references therein). ical of orogenic magmatic rocks (Fig. 28c). Apart this general rule, San Venanzo, Cupaello and Polino display Figure 29. Geological sketch map of the Neapolitan district (Roman Magmatic Province). some differences from each other. The San Venanzo olivine melilitites display a pattern strongly similar to those of ultrapotassic leucitites and plagioclase-leucitites of the Roman rocks (Figs. 16c, 18c, 20c, 22c, 24c and 26c) with comparable Ta/Nb, Nd/Sr, and Zr/Hf normalized ratios. Indeed the Cupaello clinopyroxene melilitites have the highest incompatible trace element abundances, but they do not show negative anomaly at Ba, and have reverse Ta/Nb normalized ratios (Fig. 28c). The Polino ailvikite have the lowest incompatible trace element abundances among the overall Umbrian rocks with very low K, which is a noticeable exception for carbonatite and melilite pairs, where usually the carbonatite has more than three times the incompatible trace element contents of the companion silicate rocks (e.g., Le Bas, 1987; Green et Geological sketch map of the Neapolitan volcanic dis- al., 1992; Kjarsgaard et al., 1995; Le Roex & Lanyon, trict (redrawn after Bonardi et al., 1988. 1998). D’Orazio et al. (2008) have shown that Polino ailvikite is strongly depleted in incompatible trace elements The absence of Pliocene marine sediments in the drills with respect to other similar primary mantle carbonatites. of the Campanian Plain, indicate that the southern part of the plain was above sea level during the Middle Pleisto- The Neapolitan district cene (Brancaccio et al., 1991; Cinque et al., 1993), the The Neapolitan district is the southernmost cluster of volcanoes of the Roman Magmatic Province, just south

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 46 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ period to which are dated back the older potassic and ul- 0.055 Ma (Cassignol & Gillot, 1982; Gillot et al., 1982), trapotassic rocks of the district (330 ka; Brocchini et al., followed by an intense pyroclastic activity that brought to 2001). the emplacement of the "Pignatiello" and "Citara" (0.033 The volcanic rocks cover an area as large as the entire Ma; Gillot et al., 1982) pyroclastic units, which are inter- Campanian plain, and some tephra levels originated from bedded with deposits of several minor pyroclastic erup- the largest eruptions of the Campi Flegrei and Ischia can tions. At the end of this intense period of pyroclastic ac- be found throughout the Mediterranean basin and over. tivity, whose emission centers have not been recognized, The geological evolution of the Campanian plain and the volcanism moved in the south-western sector of the is- relationships with volcanic activity have been studied in land where several monogenetic centers produced an in- detail by several authors (Ippolito et al., 1973; Cinque et tense but scattered strombolian activity with formations al., 1987, 1993; Albore Livadie et al., 1989; Brancaccio of cinder cones and lava flows. This phase protracted till et al., 1991; Romano, 1992). The volcanic complexes are about 0.018 Ma (Poli et al., 1987). The last phase of ac- made up maily of pyroclastic rocks with subordinate lava tivity, which started from 0.010 Ma b.p. and continued flows but their structures and morphological appearance till historical times (1302 A.D.), developed in the north- vary widely. eastern and northwestern sectors of the island through 1. Ischia Island several small monogenetic eruptive centers that erupted The Ischia volcanic complex emerges from the sea lava flows and pyroclastic deposits (Poli et al. 1987; with a height of 787 m. a.s.l. at Monte Epomeo and with Chiesa et al., 1988). an extension of about 40 km2 (Fig. 29). The island is The volcanic rocks of Ischia island range in composi- made up prevalently by volcanic rocks, with pyroclastic tion from shoshonites through latite to alkali trachyte and ones predominant over lavas, and lava domes. The mor- trachyphonolite (Fig. 30a), these latter rarely having a phology and geological setting of the island is controlled weak peralkaline affinity (Poli et al. 1987, 1989; Crisci et by the regional geology, and local features related to al., 1988; Di Girolamo et al. 1995; Avanzinelli et al. dome resurgence that built the Mt. Epomeo horst (Orsi et 2008; Tommasini’s unpublished data). Trachytic rocks al. 1991, 1992a; Acocella & Funiciello, 1999; Acocella are dominant throughout the volcanic sequence, whereas et al., 2001). The subaerial volcanic activity has been mafic rocks (shoshonites and latites) are more frequent in divided in five main phases (Vezzoli, 1988). The erup- the late stage of activity (<0.01 Ma), in the form of scoria tion of the Mt. Epomeo Green Tuff marked the distinc- cones aligned along preexisting structures (Vateliero, tion between the old (first two periods) and the young cy- Molara and Cava Nocelle, Fig. 29). Moreover, several cle of activity. eruptions produced volcanic rocks varying in composi- The oldest outcropping products have not been dated tion from mafic to intermediate/evolved rocks (latite/tra- and are made up by a thick sequence of pyroclastic rocks chyte; e.g., 1302 A.D., Arso lava flow, Fig. 29). Mingling and lava flows (subordinate). Their source is unknown, processes are also noticed in some recent lava flows (e.g. and they are considered to preceed the oldest dated activ- Zaro; Di Girolamo et al., 1995). The parageneses contain ity, 0.15 Ma of the lava flow of "Punta della Guardiola", clinopyroxene ± plagioclase ± olivine, with inclusions of outcropping in the southeastern and southwestern edges chromiferous spinel, and rare phlogopite. Latites have of the island (Poli et al., 1987). The former, as well as all less olivine, less An-rich plagioclase and more Fe-rich the other ages reported for Ischia are K/Ar model ages. clinopyroxene, whereas typical trachytes have sanidine During the first cycle, scattered volcanic activity devel- phenocrysts, to which hedenbergitic clinopyroxene, soda- oped on the island with the emplacement mainly of lava lite, magnetite and several accessory phases complete the domes and pyroclastic rocks, with subordinate lava mineral assemblages. Trachytes and trachyphonolites flows. The cycle ended with the "Parata" lavas dated at have also aenigmatite and sodic clinopyroxene within the 0.07 Ma (Poli et al., 1987). The second cycles started groundmasses, thus demonstrating their peralkaline na- with the eruption of the "Monte Epomeo" Green Tuff at ture (Melluso’s unpublished data).

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Figure 30. Classification and incompatible trace element No ultrapotassic rocks have been observed at Ischia characteristics of Pleistocenic to Holocenic rocks from (Fig. 30b), The Ischia mafic rocks display the lowest Ischia volcano. abundances in incompatible trace elements among the whole Roman and Italian shoshonites, but surprisingly is also the fractionation of HFE with respect to LIL elements is very weak (Fig. 30c). Troughs at Ta, Nb, and Ti as well as peaks at Th and U are negligible with respect to adjacent normalized elements (Fig. 30c). These geochemical characteristics are argued to testify the channel- ling of a within-plate component into the upper mantle source of Italian magmas (Avanzinelli et al., 2008). 2. Campi Flegrei and Procida Island The Campi Flegrei volcanic field, including Procida and Vivara islands, is a volcanic area formed by small volcanic apparata and several monogenetic volcanoes, in the form of tuff rings, tuff cones and rarely cinder cones and lava domes, cropping out outside, on the borders, and within a large polygenetic caldera formed by the eruptions of the Campanian Ignimbrite and the Neapolitan Yellow Tuff (e.g., Rosi et al., 1983; Armienti et al., 1983; Di Girolamo et al., 1984; Rosi & Sbrana, 1987; Orsi et al., 1992, 1995, 1996a, 1999; Cole & Scarpati, 1993; Di Vito et al., 1999; De Vivo et al., 2001; Ort et al., 2003). The oldest volcanic activity is represented by the pre- Campanian Ignimbrite deposits, which are found as loose remnant cropping out outside and on the borders of the Campanian Ingnimbrite caldera, and it dates back till ~0.08 Ma (Pappalardo et al., 1999) (Fig. 29). Other ignimbritic deposits are found in the Campanian Plain with 40Ar-39Ar ages of ~0.21 Ma (De Vivo et al., 2001) and ~0.29 Ma (Rolandi et al., 2003). The large volume Cam- panian ignimbrite (Fisher et al., 1993; Rosi et al., 1996: ca. 300 km3 of dense rock equivalent magma - D.R.E.), whose proximal products are found at Procida, Monte di Procida, Giugliano, Quarto, Cuma, bottom of Camaldoli and San Martino Hills have been produced by a large Classification and geochemical characteristics of the eruption, on which several age data were published Ischia volcanic rocks. A) Total Alkali-Silica (TAS) clas- (40Ar-39Ar ages: ~0.037 Ma, Deino et al., 1994; ~0.039 sification diagram (Le Maitre, 2002). B) K2O wt.% vs. Ma, De Vivo et al., 2001; ~0.038 Ma, weighted average SiO2 wt.% classification diagram with reported the grid for orogenic volcanic rock suites (Peccerillo & of 10 samples in Fedele et al., 2008). An intense volcanic Taylor, 1976). C) Incompatible trace element patterns activity occurred after the formation of the Campanian for mafic volcanic rocks normalised to the primordial Ignimbrite caldera, with the formation of pyroclastic de- mantle values of Sun & McDonough (1989). Data from posits from several volcanic centers. A second large Poli et al. (1987, 1989), Crisci et al. (1988), Di Girolamo et al. (1995), Avanzinelli et al. (2008) Tommasini’s un- eruption dates back at 0.015 Ma (Deino et al., 2004) with published data). the emplacement of the Neapolitan Yellow Tuff (Cole & Scarpati, 1993; Wohletz et al., 1996), which has been

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 49 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ estimated at 12 km3 D.R.E (Rosi & Sbrana, 1987). The Figure 31. Classification and incompatible trace element most recent volcanic activity, placed within the Neapoli- characteristics of Holocenic volcanic rocks from Campi Flegrei and Procida. tan Yellow Tuff caldera and on its borders, dates back to 1538 A.D. with the eruption of Monte Nuovo (e.g., de Vi- ta et al., 1999; Isaia et al., 2004; D’Oriano et al., 2005). At present, only fumarolic and bradeyseismic activity is ongoing. The Campi Flegrei volcanic rocks are predominantly of pyroclastic nature and vary in composition from shoshonitic basalts to trachytes and trachyphonolites (Fig. 31a), belonging to the shoshonitic series (Fig. 31b); some trachyphonolites are weakly peralkaline (e.g., Ar- mienti et al., 1983; Villemant, 1988; Beccaluva et al., 1990; Civetta et al., 1991a; Melluso et al., 1995; Pappa- lardo et al., 1999, 2002; D’Antonio et al., 1999b; Paone, 2004). The most mafic compositions are present at Proci- da volcano as lava clasts in phreatomagmatic eruptions and scoriae from monogenetic activity (e.g., D’Antonio et al., 1999a; De Astis et al., 2004; Fedele et al., 2006). Differentiated compositions are rarely found in the mainland within the Campi Flegrei volcanic field (e.g., Con- cola, Cigliano, Montagna Spaccata, Nisida) and they have been achieved by open system shallow level differentiation processes (e.g., Pappalardo et al., 2002). The majority of the Campi Flegrei volcanic rocks are trachytes and trachyphonolites, including the chemically zoned Campanian Ignimbrite and Neapolitan Yellow Tuff deposits (e.g., Scarpati et al., 1993; D’Antonio et al., 1999a, Fedele et al., 2008). Evidence of interaction between mafic and evolved magmas is clearly seen in most pyroclastic eruptions (Fedele et al., 2009), and is more frequent in the latest stage of activity (<0.015 Ma), where less evolved compositions are frequently found. Mineralogically, the primitive basalts have typical phenocryst assemblage formed mainly by Fo-rich olivine with chromiferous spinel inclusions, with Mg-rich clinopyroxene, and Ca-rich plagioclase. Latites have more Na- rich plagioclase, with clinopyroxene, phlogopite, magnet- Classification and geochemical characteristics of the ite phenocrysts and microlites, whereas trachytes have Campi Flegrei and Procida volcanic rocks. A) Total Al- the typical assemblage K- to Na-rich sanidine, Na-plagio- kali-Silica (TAS) classification diagram (Le Maitre, 2002). B) K2O wt.% vs. SiO2 wt.% classification dia- clase, Fe-rich clinopyroxene, Fe-rich amphibole and sev- gram with reported the grid for orogenic volcanic rock eral accessoriy phases, with additional groundmass or suites (Peccerillo & Taylor, 1976). C) Incompatible microphenocryst sodalite ± nepheline. Mixed phenocryst trace element patterns for mafic volcanic rocks nor- assemblages are frequently found in both lava domes and malised to the primordial mantle values of Sun & McDonough (1989). Data from Pappalardo et al. pyroclastic rocks (e.g., Fedele et al., 2008). (1999, 2002), D’Antonio et al. (1999b), Fedele et al. (2006, 2008), Avanzinelli et al. (2006, 2008).

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Figure 32. Classification and incompatible trace element Incompatible normalized trace element patterns of the characteristics of Pleistocenic to Holocenic volcanic rocks mafic volcanic rocks from Campi Flegrei and Procida from Somma-Vesuvius volcano. have mild enrichment with smooth fractionation of large ion lithophile with respect to high field strength elements (Fig. 31c). Indeed Ta and Nb troughs are extremely smoother with respect to other Roman volcanoes. The Ba trough is absent, whereas the Hf trough is more pro- nounced (Fig. 31c). It is important to note, as in the rest Neapolitan district the relatively low U and Th abundances with respect to the other Italian ultrapotassic and related igneous rocks, with also peculiar U/Th ratios (Avan- zinelli et al., 2008). 3. Somma-Vesuvius The Somma-Vesuvius volcanic complex is actually formed by two main volcanic edifices separated by two calderas: the Monte Somma composite volcano, disrup- ted by several pyroclastic eruptions which formed at least two calderas in the last 0.022 Ma (the Somma caldera s.s. and the Piano delle Ginestre calderas), and the Vesuvius s.s., a cone mostly formed by juxtaposition (and disruption) of volcanic rocks erupted from the 79 A.D. (Pompei eruption) and the 1944 A.D. last eruption. Some eccentric cones and lava domes are recorded throughout the activity (e.g., Santacroce, 1987; Rosi et al., 1993; Principe et al., 2004; Di Renzo et al., 2007; Cioni et al., 2008; San- tacroce et al., 2008). The oldest volcanic activity has been found as leucitite-bearing lavas in a drill at Trecase and dated at about 0.4 Ma (Brocchini et al., 2001). The Vesuvius rocks lack of primitive magma compositions (Table 7), due to a more or less efficient stoping in several shallow depth reservoirs (e.g., Civetta et al., 1991b, 2004; Santacroce et al., 1993; Cioni et al., 1995; Del Moro et al., 2001; Fulignati et al., 2004; Gurioli et al., 2005; Morgan et al., 2006; Scaillet et al., 2008). There is clear evidence of shift of magmatic compositions with time (Joron et al., 1987; Cioni et al., 2008, and references therein). The bulk of the Somma volcanic Classification and geochemical characteristics of the rocks are less undersaturated in silica, and range in com- Somma-Vesuvius volcanic rocks. A) Total Alkali-Silica position from leucite-bearing trachybasalts to leucite lat- (TAS) classification diagram (Le Maitre, 2002). B) K2O ites to trachytes, whereas the more recent volcanic rocks, wt.% vs. SiO2 wt.% classification diagram with reported the grid for orogenic volcanic rock suites (Pecce- in the form of lava flows and juvenile products of plinian rillo & Taylor, 1976). C) Incompatible trace element eruptions, range in composition from leucite basanite and patterns for mafic volcanic rocks normalised to the leucite tephrite to phonolite (Fig. 32a). All the Somma- primordial mantle values of Sun & McDonough (1989). Vesuvius mafic volcanic rocks are silica undersaturated, Data from Joron et al. (1987), Ayuso et al. (1998), Di Rienzo et al. (2007), Avanzinelli et al. (2008) Melluso’s and belong to the ultrapotassic plagioclase-leucititic vol- unpublished data). canic series (Fig. 32b), differently from the volcanic rocks of Campi Flegrei volcanic field and Ischia volcanic

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 51 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ complex, indicating completely independent magma res- volcano, with the emission of the Melfi haüynophire ervoirs and feeding systems (e.g., Cortini & Hermes, (0.56 Ma, Bonadonna et al., 1998; 0.57 Ma, Villa & 1981; Joron et al., 1987; Caprarelli et al., 1993; Villem- Buettner, 2009) and Piano di Croce lavas, and the begin- ant et al., 1993; Ayuso et al., 1998; Paone, 2006; Cioni et ning of the sector collapse along the curved faults of the al., 2008 and references therein). Recently, Iacono Mar- Valle dei Grigi (Guest et al., 1988; Principe & Giannan- ziano et al. (2007), resurrected the old hypothesis by Ritt- drea, 2006). The volcanic and tectonic activity of the man (1933) of shallow level carbonate assimilation to ex- Vulture area has been sealed by a thick paleosoil (Schiat- plain the transition from leucite-free shoshonitic Somma tarella et al., 2005). Volcanic activity renewed later in compositions to ultrapotassic leucite-bearing recent activ- small centres along fractures and it is characterised by ity. small carbonatitic lava flows and explosion craters with Similarly to the other Neapolitan district volcanoes, formation of the Lago Grande and Lago Piccolo maars incompatible normalized trace element patterns of Som- (Stoppa & Principe, 1997; Principe & Giannandrea, ma-Vesuvius mafic rocks still have a very marked frac- 2006). The magmatic fraction of a surge from the Laghi tionation of LILE with respect to HFSE (Fig. 32c), with di Monticchio volcanic field gives an age of about 0.13 troughs Ta, Nb, and Ti, no Ba anomaly and inversion of Ma (Brocchini et al., 1994). The Toppo del Lupo lavas Th enrichment with occurrence of a very small trough are likely part of this monogenetic activity (D’Orazio et (Fig. 32c). In terms of trace element distribution the vol- al., 2007, 2008). All reported ages for this magmatic canic rocks of the Neapolitan district display some simi- Province are 40Ar-39Ar ages. larities with the volcanic rocks of the Lucanian Magmatic Province (i.e., Monte Vulture, see below), but Peccerillo Figure 33. Geological sketch map of the Monte Vulture volcano (Lucanian Magmatic Province). (2001, 2005a) and Peccerillo & Alagna (2010, this volume) suggested a geochemical connection with Strombo- li volcanic rocks (Aeolian Islands), which are, however, characterized by distinctly lower silica undersaturation.

Lucanian Magmatic Province: the Mt. Vulture and Monticchio lakes volcanoes The Lucanian Magmatic Province is made up by the Monte Vulture and Monticchio nested volcanoes, with few small eccentric explosive monogenetic centres along the Ofanto valley and at Ripacandida. The volcanism of this province is located east of the Apennine system, not far from the Apulian foreland (Fig. 11). The Monte Vul- ture volcano lies on a structural high made up by Meso- Cenozoic units of the substratum with Pliocene continental sediments on their top (Schiattarella & Beneduce, 2006; Giannandrea et al., 2006). The volcanic activity at Vulture-Monticchio nested volcanoes (Fig. 33) developed entirely within the Pleistocene starting at about 0.74 Ma (Villa & Buettner, 2009). The main stratovolcano represented by the Rionero and, mainly, by the Vulture-

San Michele subsynthems (Principe & Giannandrea, Geological sketch map of the Lucanian volcanic dis- 2006) was built up between ~0.67 and ~0.6 Ma (Brocchi- trict redrawn after Giannandrea et al., 2006.. ni et al., 1994; Villa & Buettner, 2009). At the end of this period volcanic activity produced lava flows from parasitic vents along the north and north-eastern side of the

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Figure 34. Classification and incompatible trace element The bulk of the erupted products mostly belong to a characteristics of Pleistocenic rocks from Lucanian basanite-tephrite-phonolite series (Fig. 34a; Table 8), Magmatic Province. with mafic products (basanites and tephrites) dominating in both lavas and pyroclastic rocks (e.g., De Fino et al., 1986; Beccaluva et al., 2002). More silica undersaturated rocks, though minor in volume, are typical of this volcanic complex (Hieke Merlin, 1964, 1967). Melilitites, haüynites, haüyne-bearing leucitites are also found at the end of the Monte Vulture volcanic activity in the form of dikes, plugs and lava flows in the north-western flank of the volcano (Fig. 33). On the other hand, trachyphonolites are found as dykes in the neighbourings of the volcanic complex, and may be representatives of an earlier, and less silica undersaturated stage of activity (Melluso et al., 1996; Beccaluva et al., 2002). The typical phenocryst mineralogy of basanites and tephrites is composed by Fo-rich olivine (with chrome spinel inclusions), Ca- rich clinopyroxene, haüyne and leucite, to which Ca-rich plagioclase, amphibole, biotite and Fe-Ti oxides can be associated (Melluso et al., 1996; Caggianelli et al., 1990). Typical phonolites have phenocrysts of sanidine, haüyne, Fe-rich clinopyroxene, magnetite and garnet in a groundmass with additional nepheline. The melilite-bearing rocks are plagioclase-free rocks with clinopyroxene and haüyne phenocrysts; melilite is present as phenocryst or as groundmass phase, along with leucite, nepheline, Ti-rich garnet, magnetite, mica and perovskite (Melluso et al., 1996). The Monticchio lakes volcanic activity was mainly characterized by pyroclastic deposits related to explosive and hydromagmatic activity. A small carbonatitic lava flow has been also found at Toppo del Lupo (e.g., Stoppa and Principe, 1997; D’Orazio et al., 2007, 2008; Stoppa et al., 2008). Within the hydromagmatic units round lapilli tuffs units with ejecta of intrusive carbonatites and mantle nodules are also found (e.g., Jones et al., 2000; Rosatelli et al., 2000; Downes et al., 2002). The carbo- Classification and geochemical characteristics of the natic lava flows and pyroclastic rocks have olivine, mon- Lucanian volcanic rocks. A) Total Alkali-Silica (TAS) ticellite, clinopyroxene, melilite, magnetite, amphibole classification diagram (Le Maitre, 2002). B) K2O wt.% and phlogopite, along with primary calcite laths (D’Ora- vs. SiO2 wt.% classification diagram with reported the grid for orogenic volcanic rock suites (Peccerillo & zio et al., 2007). K2O contents of the volcanic products Taylor, 1976). C) Incompatible trace element patterns decrease with time passing from Monte Vulture to Mon- for mafic volcanic rocks normalised to the primordial ticchio volcanoes. Sodic compositions are also found mantle values of Sun & McDonough (1989). Data from Hieke Merlin (1967), De Fino et al. (1986), Melluso et among lapilli tuffs of the Monticchio lake activity (Avan- al. (1996), Beccaluva et al. (2002), Downes et al. zinelli et al., 2008, 2010). In addition the Lucanian vol- (2002), De Astis et al. (2006), D’Orazio et al. (2007, canic rocks have an increasing content of incompatible 2008), Stoppa et al. (2008), Avanzinelli et al. (2008, elements, coupled to a decreasing fractionation of HFSE 2010).

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 54 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ with respect to LILE, with time passing from Monte Vul- upwelling through the upper crust (Acocella & Funiciel- ture to Monticchio products (Fig. 34c). This feature has lo, 2006). been interpreted by De Astis et al. (2006) as an increas- Middle-Upper Pleistocene volcanoes of the Tyrrheni- ing contribution of asthenospheric foreland mantle in the an margin, belonging to the Roman and Lucanian Mag- genesis of Lucanian rocks from slab tears in the Adriatic matic provinces, show a variety of morphologies and plate subducted beneath the Italian Peninsula. A partial eruption styles. Volumes involved are in the order of sev- melting during adiabatic ascent of the upper mantle eral hundreds of km3 for each volcanic complex and of source has been evidenced for the final Monticchio lake several thousands of cubic kilometres for the whole vol- rocks (Avanzinelli et al., 2008, 2010). canic belt (Table 9). All volcanoes, apart the Middle Lat- in Valley monogenetic ones, are associated with calderas, Volcanic structures of the Roman and Lucanian which are formed almost coevally, then suggesting a fur- Magmatic Provinces ther structural and geodynamic control on volcanism. Monogenetic volcanism and dyking prevails in the Very highly explosive volcanoes erupted several inter- Western Alps, Corsica and Tuscan Magmatic provinces, mediate to large volume ignimbrites and are character- whereas volcanic edifices, ranging from flat ignimbrite ised by large, polyphased calderas and large ignimbritic shields to steep stratovolcanoes, prevail within the Ro- plateaux. These complexes have been classified as cal- man and Lucanian magmatic provinces. This characteris- dera complexes and they are, from north to south: the tic is a direct consequence of the volume of magma pro- Bolsena and Latera volcanoes in the Vulsinian district, duced by the mantle source(s) but also of the tectonic re- the Bracciano and Sacrofano volcanoes in the Sabatian gime acting during magma emplacement. There is a gen- district, the Vulcano Laziale volcano in the Colli Albani eral consensus about the fact that Pleistocene volcanoes district, the Campi Flegrei volcano in the Neapolitan dis- of the Roman and Lucanian Magmatic Provinces are fav- trict. On the other hand, several composite volcanoes oured by the extensional post-orogenic tectonics. Indeed, characterized by a well formed stratocone are also locations and spacing on a crustal scale of the Roman present either as main edifice or as a secondary edifice volcanoes is ubiquitously related to intersection between during post caldera activity. At the former category be- NW-trending and NE-trending transverse extensional long the Vico, Roccamonfina, Ventotene, Ischia, Somma, structures. This has been recorded in almost all volcanic and Vulture volcanoes, whereas to the latter one belong districts of the Roman province: Vulsini (Barberi et al. the Monte delle Faete, the intracaldera stratocone of Colli 1984), Vico (Sollevanti 1983; Bear et al., 2009a,b), Saba- Albani, and the Vesuvius (Table 9). tini (De Rita et al., 1983, 1996), Colli Albani (Giordano Almost all the Roman and Lucanian volcanoes erup- et al., 2006), Middle Latin Valley (Sani et al., 2006; ted intermediate volume ignimbrites, which brought to Boari et al., 2009b), Roccamonfina (Giordano et al., the formation of small summit collapse composite calde- 1995; De Rita & Giordano, 1996), Campi Flegrei (Scan- ras (e.g., Vico, Roccamonfina, Ischia, Somma-Vesuvius done et al. 1991; Orsi et al., 1996a), and Somma-Vesu- and Vulture). Ischia volcanic complex hosts the only re- vius (Santacroce, 1987; Bianco et al., 1998) volcanoes. surgent caldera (Orsi et al., 1991; Acocella & Funiciello Furthermore, NE-trending faults are transfer structures of 1999). Sector collapses associated with gravitational in- the regional NW-trending extensional faults, and seldom stability of the stratovolcanoes have also been described inherited from NE-trending transfer structure formed dur- at Roccamonfina (De Rita & Giordano, 1996) and Vul- ing the Apennine compression. For this reason NE-trend- ture (Guest et al., 1988) volcanoes. ing faults are thought to bear a more vertical dip than Latest stages of activity of many of the Roman and NW-trending faults which instead have been highlighted Lucanian volcanoes are associated to phreatomagmatism, as low-angle normal faults in several seismic studies which produced tuff rings and tuff cones, but maar vol- (Collettini et al., 2006). NE-trending fractures and faults canism has been also recorded (e.g., Albano lake and may play therefore a determinant role to magmatic melts Monticchio lakes, Figs. 21 and 33).

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The Mt. Amiata volcano, which is the northernmost 2005a), but a series of petrologic and geochemical evi- Pleistocene volcanoes of this belt (Fig. 11), is somewhat dence related the triggering of the Mt. Amiata volcanic intriguing. For long time it was thought to belong to the activity to the arrival of leucite-bearing Roman magmas Tuscan Magmatic Province (e.g., Marinelli, 1961; Pecce- at shallow level (van Bergen et al., 1983; Conticelli et rillo et al., 1987; Innocenti et al., 1992; Peccerillo, al., 2010c).

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Figure 35. Nd-Sr isotopic variations for the Western Alps, Tuscan province. The interaction between the two mag- Western Tyrrhenian Sea (Corsica) and Tuscan Magmatic mas brought the extrusion of highly viscous crystal-rich provinces. Tuscan magmas together with mingled Roman magmas in which crystallization of leucite was suppressed by the interaction process with the high silica magmas (Conti- celli et al., 2010c). This explains the very recent time of extrusion, which is clearly associated with the Roman Magmatic Province volcanism, but also the high aspect ratios of lava flows and the exogenous dome formation (Ferrari et al., 1996). A characteristic that has been never recorded in the volcanoes of the Roman Province, but re- calling the Pliocene magmatism related with the Tuscan magmas such as the Tolfa-Manziana-Ceriti dome complexes and the Monte Cimino Volcanic complex.

Sr, Nd and Pb Isotopes Italian ultrapotassic rocks and associated shoshonites, high-K calc-alkaline and calc-alkaline igneous rocks have extremely variable radiogenic isotope compositions (e.g., Tables 2-8), displaying a geographic variation firstly from West to East and later from North-West to South- West (see fig. 10 in Conticelli et al., 2007). The observed isotope variation covers almost the entire spectrum of mantle and upper crustal values, compli- cating the interpretation of the petrogenetic grid of Italian ultrapotassic and associated shoshonites and calc-alkaline rocks (e.g., Hawkesworth & Vollmer, 1979; Vollmer & Hawkesworth, 1981; Vollmer, 1989; Conticelli et al., 2002, 2007; Gasperini et al., 2002; Bell et al., 2004; Mar- telli et al., 2004; Peccerillo, 2004; Avanzinelli et al., 2008). 87 86 Sr/ Sri values range from 0.70522 for a basanite at Monte Vulture Volcano (Avanzinelli et al., 2008) to 0.71883 for the Rio Rechantez minette in the Western 143 144 Alps Oligocene province (Owen, 2008); Nd/ Ndi values range from 0.512712 for a basanite at Monte Vul- ture Volcano (D’Orazio et al., 2007) to 0.511991 for the Data from Venturelli et al. (1984), Peccerillo et al. Rio Rechantez minette in the Western Alps Oligocene (1988), Pinarelli (1991), Conticelli et al. (1992, 2002, 2007, 2009a, 2010c, 2010d), Conticelli (1998), Ca- province (Prelevic et al., 2008; Conticelli et al., 2009a). 143 144 deaux et al. (2005), Peccerillo & Martinotti (2006), Initial Nd/ Nd values show a strong negative cor- Owen (2007), Prelevic et al. (2008), Avanzinelli et al. relation with initial 87Sr/86Sr (Figs. 35, 36, and 37), al- (2008). though a decoupling of the correlation is observed between leucite-bearing and leucite-free trends (i.e., Conti- Uprising silica-undersaturated magmas, potentially celli et al., 2002). The most primitive rocks of each mag- leucite-bearing, have been intercepted by long-living matic province define trends with isotopic values that magma chamber filled by silica-saturated and extremely vary regularly passing from ultrapotassic mafic terms to differentiated shoshonitic to calc-alkaline magmas of the calc-alkaline ones through shoshonites (Figs. 35 and 36),

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 57 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ with the former having the most crust-like values. A data; Melluso’s unpublished data; Tommasini’s un- strong correlation between isotopic values and the abun- published data. dances of K, Rb, Sr, Ba and most incompatible trace ele- Within the Roman Magmatic Province two different ments is present (Cox et al., 1976; Conticelli et al., sectors can be distinguished based on radiogenic iso- 2009a). topes: the rocks from the districts of the northern sector Figure 36. Nd-Sr isotopic variations for the Amiata Volcano, (i.e., Latian districts: Vulsini, Vico, Sabatini, Colli Alba- Roman and Lucanian Magmatic provinces. ni, Middle Latin Valley, and Roccamonfina; Figs. 1 and 87 86 143 144 11) show higher Sr/ Sri and lower Nd/ Ndi values relatively to the rocks of the Neapolitan district (Fig. 37), the southernmost cluster of volcanic apparata (Figs. 1 and 11). Post-caldera shoshonites and sub-alkaline rocks of the southernmost Latian district (i.e., Roccamonfina volcanoes) show intermediate values between Latian and Neapolitan rocks (Fig. 37).

Figure 37. Nd-Sr isotopic variations for the Roman Magmatic Provinces with fields for each single district.

Data from Conticelli et al. (1987, 1991, 1997, 2002, 2007, 2009b), Ayuso et al. (1998), Pappalardo et al. (1999, 2002), D’Antonio et al. (1999b), Perini et al. (2000, 2003, 2004), Gasperini et al. (2002), Di Rienzo et al. (2007), Avanzinelli et al. (2008), Boari et al. (2009a,b), Tommasini’s unpublished data.

The same geographic variation can be onserved in Pb, Hf, and He isotopes. Lead isotopes display single correlation trends for each magmatic province with the ultrapotassic terms, either leucite-bearing or –free, at the most radiogenic end. Each trend runs parallel to the other ones Data from Conticelli et al. (1987, 1991, 1997, 2002, 2007, 2009b), Ayuso et al. (1998), Pappalardo et al. (e.g., Conticelli et al., 2009b; Boari et al., 2009b) (Fig. (1999, 2002), D’Antonio et al. (1999b), Perini et al. 38); the trend of Western Alps Oligocene magmatic (2000, 2003, 2004), Downes et al. (2002), Gasperini et 206 204 province lies at the lowest Pb/ Pbi values whilst that al. (2002), De Astis et al. (2006), Di Rienzo et al. (2007), D’Orazio et al. (2007, 2008), Avanzinelli et al. (2008, of the Lucanian Magmatic Province at the highest (Fig. 2010), Boari et al. (2009a,b), Conticelli’s unpublished 38).

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87 86 143 144 204 Figure 38. Sr/ Sri, Nd/ Ndi, and 208Pb/ Pbi vs. Strontium and Neodimium. Indeed the Corsican rocks 206 204 Pb/ Pbi for the Italian ultrapotassic rocks. depict opposite trends to those observed in the other magmatic provinces. Zenobito alkali basalts plot as an offset with respect to the Italian array (Fig. 38) toward the isotopic composition of Late/Middle Miocene-Quaternary volcanic rocks of Sardinia, and in general toward a depleted mantle source (e.g., Avanzinelli et al., 2009, and references therein). Bell et al. (2004) argued that the general trend of the Italian rocks points toward a FOZO compo- 87 86 206 204 nent in the Sr/ Sri vs. Pb/ Pbi diagram (Fig. 38). Indeed, as a whole, Italian rocks fill the gap between upper crustal composition and FOZO (Hart et al., 1992) passing through the isotopic composition of EM II end- member (Zindler & Hart, 1986), which is believed to represent a recycled sedimentary component. In figure 38 most of Italian potassic and ultrapotassic products plot between upper crustal composition and EM II with the most ultrapotassic compositions (i.e., lamproite, kamafugite and leucitite) closest to thye upper crustal composition. FOZO isotope compositions are only approached by volcanic rocks from magmatic suites south of the 41st parallel, which also points toward the isotope composition of anorogenic cretaceous alkali basalts occurring on the Apulian foreland (Fig. 38). A less-depleted asthenospheric mantle source has been proposed for the southernmost sector of Italian magmatism (e.g., Beccaluva et al., 1991; Avanzinelli et al., 2009). Similar isotopic compositions are also reported for calc-alkaline rocks from the Aeolian Arc (e.g., Francalanci et al., 1993, 2007; Pec- cerillo, 2001, 2005a; Tommasini et al., 2007). Evidence for a strongly anomalously enriched upper mantle for the source of ultrapotassic magmas is also 176 177 highlighted by the values of Hf/ Hfi (Fig. 39), which vary from values typical of lamproitic magmatism (e.g., Prelevic et al., 2010) to values similar to astenospheric Data from Conticelli et al. (1987, 1991, 1997, 2002, mantle reservoir in the region below the 41st parallel (i.e. 2007, 2009a, 2009b, 2010c, 2010d), Ayuso et al. (1998), Conticelli (1998), Pappalardo et al. (1999, Neapolitan district). Indeed, eHfT values are as low as 2002), D’Antonio et al. (1999b), Perini et al. (2000, -13 in lamproitic rocks from Western Alps, Western Tyr- 2003, 2004), Downes et al. (2002), Cadeaux et al. rhenian Sea, and Tuscany (Prelevic et al., 2010) increas- (2005), De Astis et al. (2006), Peccerillo & Martinotti ing to values between -9 and -7 in shoshonitic rocks asso- (2006), Di Rienzo et al. (2007), D’Orazio et al. (2007, 2008), Owen (2007), Prelevic et al. (2008), Stoppa et ciated to lamproites (Gasperini et al., 2002; Prelevic et al. (2008), Avanzinelli et al. (2008, 2010), Boari et al. al., 2010), and between -8.1 and -6.2 in the leucite bear- (2009a,b), Cadeaux & Pinti (2009), Melluso’s unpub- ing rocks of the Latian districts of the Roman province lished data; Tommasini’s unpublished data. (Gasperini et al., 2002), up to values of -0.5 and -0.2 for The volcanic rocks of the of the Westrern Tyrrhenian the rocks of the Neapolitan district (Gasperini et al., Sea Magmatic Province (Corsican) represent an excep- 2002; Tommasini’s unpublished data). A strong negative 176 177 87 86 tion to the observed array of lead isotopes versus those of correlation between Hf/ Hfi and Sr/ Sri reinforce

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187 188 87 86 the hypothesis of the recycling of an upper crustal com- Figure 40. Os/ Osi vs. Sr/ Sri for the Italian ponent in the mantle source of the ultrapotassic Italian ultrapotassic rocks. magmas (e.g., Gasperini et al., 2002; Prelevic et al., 2010).

177 87 86 Figure 39. 176Hf/ Hfi vs. Sr/ Sri for the Italian ultrapotassic rocks.

Data from Conticelli et al. (2007).

Origin of the Italian Magmatism The origin of Italian potassic and ultrapotassic rocks and of their peculiar trace elements and isotopic signa- Data from Gasperini et al. (2002), Prelevic et al. (2010), tures were the object of a scientific debate centered on Tommasini’s unpublished data. two main possible mechanisms: a) within-plate origin, possibly linked to partial melting of an up-rising mantle He isotopes performed on fluid inclusions within oli- plume (e.g., Vollmer & Hawkesworth, 1981; Vollmer, vine and clinopyroxene crystals from rocks of the Tuscan 1990; Ayuso et al., 1998; Castorina et al., 2000; Gasperi- and Roman magmatic provinces (Martelli et al., 2004) ni et al., 2002; Bell et al., 2004); b) orogenic to post-oro- add further constraints on the nature of the mantle sour- genic origin, related to partial melting of the sub-conti- ces of these magmas. 3He/4He values are significantly nental lithospheric metasomatised mantle at a destructive lower than MORB and display a negative correlation plate margin, with important contributions from recycled with 87Sr/86Sr (measured either on whole rocks or clino- sediments (e.g., Cox et al., 1976; Peccerillo, 1985, pyroxene crystals). Martelli et al. (2004) suggested the 2005a; Rogers et al., 1986; Beccaluva et al., 1991; Conti- occurrence of a binary mixing between an asthenospheric celli & Peccerillo, 1992; Downes et al., 2002; Bianchini component, similar to an HIMU ocean island basalt, and et al., 2008). an enriched in radiogenic isotopes upper mantle compo- Some of the authors suggesting the within-plate origin nent, metasomatised with recycled sediments. also point out the need for an increasing influence of an Recycled sediments within the upper mantle source of upper crustal geochemical component northward, al- ultrapotassic magmas has been also pointed out on the though no convincing reasons have been provided to ex- basis of 187Os/188Os vs. 87Sr/86Sr values (Fig. 40). In- i i plain it in the frame of a within-plate, extensional geody- deed, significant amounts of recycled crustal material (up namic setting (e.g., Hawkesworth & Vollmer, 1979; to 65% for the most enriched lamproites of the Tuscan Vollmer, 1990; Gasperini et al., 2002; Bell et al., 2004). Magmatic Province) within the upper mantle source are In the anorogenic ‘plume-related’ model the crustal sig- required for the genesis of ultrapotassic lamproitic and nature is generally attributed to shallow level magma kamafugitic magmas (Conticelli et al., 2007). contamination processes. The high extent of shallow level crustal contamination required to reproduce the Italian ultrapotassic magmas (> 70 vol. % to gives the lamproitic isotopic signatures) seems unlikely to occur at shallow

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 60 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ level without suffering extensive crystallization of mafic Subduction-related metasomatism phases. This would have decisely decreased the MgO, Ni, The isotopic charateristics discussed above matches and Cr contents of the mafic rocks bringing them on the well with the incompatible trace element distributions differentiated felsic side (Conticelli, 1998; Turner et al., ubiquitously shown by the volcanic rocks of each mag- 1999; Murphy et al., 2002). On the contrary, the most ul- matic province. It is generally thought that fractionation trapotassic rocks from each magmatic province (i.e. of High Field Strength Elements (HFSE) with respect to lamproites, kamafugites and lucitites), which also display Large Ion Lithophile Elements (LILE) is a typical char- the highest crustal signature, are the ones bearing the acteristic beared by orogenic magmatic suites (e.g., Pec- highest abundances in MgO and compatible trace ele- cerillo, 1985; Hofmann, 1996, Hoefs, 2010) and that Pb ments (Tables 2-8). In addition these rocks have liquidus peaks are generated by sediment recycling within the up- highly forsteritic olivine, which does show textural char- per mantle (Avanzinelli et al., 2008). The relative immo- acteristics typical of extra olivine from cumulus process- bility in aqueous fluids of incompatible high field es. In addition, a proportion of assimilated crust higher strength elements and Th with respect to large ion litho- than 40 vol. % would rapidly freeze the magma, stalling phile ones has long been used to distinguish between the its ascent and causing it to crystallise completely. In sum- roles of fluids and melts during metasomatism (e.g., mary, even a small amount of crustal contamination Hawkesworth et al., 1990; Keppler, 1996; Elliott et al., would result in rapid crystallization and fractionation of 1997; Elliott, 2003; Kessel et al., 2005). Conversely, the mafic minerals. MgO, FeO, Ni, Sc, and Cr contents budget of other trace elements such as Th, is controlled in would dramatic decrease in the contaminated magma arc rocks by sediment recycling (e.g., Elliott et al., 1997; with no further enrichment in K2O (Conticelli, 1998; Plank & Langmuir, 1998; Tommasini et al., 2010). High Turner et al., 1999; Murphy et al., 2002). Th concentrations, Th/Nb and Th/REE ratios in subduc- Avanzinelli et al. (2008) recently reported a compre- tion-related volcanic rocks are interpreted as representa- hensive study of U-Th disequilibria on the youngest Ital- tive of recycled sediments. The comparison of these ra- ian rocks with the aim of investigating the mechanism of tios with subducted sediments have suggested that the source melting. The authors excluded the possibility of latter are recycled as melts (e.g., Elliott et al., 1997; the plume-related genesis, in particular of a plume up- Hawkesworth et al., 1997; Class et al., 2000; Elliott, welling from a slab window located under the Neapolitan 2003; Plank, 2005) enriched in Th and incompatible trace 238 area, on the strength of significant U-excess measured elements, but still depleted in HFSE, probably due to the in the volcanic rocks of the Neapolitan district of the Ro- occurrence of residual rutile during sediment partial melt- 238 man Province. In fact, U-excess is widely accepted as ing (e.g., Elliott et al., 1997; Tommasini et al., 2007). one of the key evidence of subduction-related magma At sub-arc temperatures and pressures the physical genesis (e.g., Elliott et al., 1997; Hawkesworth et al., distinction between fluids and melts is lost above the 1997). The occurrence of such excesses only in Neapoli- ‘second critical end point of saturation’ (e.g., Kessel et tan rocks is ascribed to the recent addition of a U-rich al., 2005; Hermann et al., 2006) where they converge to fluid component, which is also expected to act as a trig- a ‘supercritical liquid’, but ‘fluid’-like and ‘melt’-like ger for magmatism. The lack of any significant disequili- liquids can still be distinguished using the relative pro- bria in the Latian districts (Roman Magmatic Province) portion of H2O and solute contents, depending upon the and Amiata rocks (Tuscan Magmatic Province) is also in- T°C of ‘supercritical liquid’ formation (e.g., Hermann et consistent with adiabatic melting of a deep-seated mantle al., 2006). Klimm et al. (2008) showed that the trace ele- 230 plume, which would produce significant Th excesses ment budget of metasomatic agents released by the basal- (Avanzinelli et al., 2008). On the other hand, significant tic subducting crust at at 2.5 GPa, regardless of whether 230 Th- excesses, an indicator of adiabatic melting, have they are ‘fluids’ or ‘supercritical liquids’, depends upon only been measured in a sample from the Monticchio the solubility of accessory phases such as allanite and lakes volcanism, in the Lucanian Magmatic Province monazite (controlling REE and Th and U) and rutile (de- (Avanzinelli et al., 2008, 2010). termining the Ti and Nb contents). At normal slab/mantle interface temperatures these accessory phases are stabi- lised in the residuum during slab melting, strongly

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 61 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ sequestering REE, Th, (in allanite and/or monazite) and Figure 41. Ba/Th vs. Th/Nb for the Italian ultrapotassic Ti and Nb (in rutile) from the metasomatic liquids. The rocks. resulting metasomatic liquid is enriched only in the elements not hosted in the residual accessory phases (Cs, Rb, Ba, K, Pb, Sr and U over Th), perfectly reflecting the widely accepted composition of the slab derived aqueous ‘fluids’. With increasing temperature or/and pressure the metasomatic liquids incorporate higher amounts of sol- utes (i.e. ‘melts’), and the solubility of allanite, monazite and rutile increases until they are eventually eliminated from the residue with Th, and REE released into the melts (Hermann, 2002; Kessel et al., 2005; Klimm et al., 2008). However, until over-saturated, allanite and rutile will completely control the REE, Th, U (allanite) and Ti, Nb (rutile) content of the sedimentary ‘melts’. Similar conclusions have been reached by Skora & Blundy (2010) starting from radiolarian clay-rich sediments. Allanite and monazite have partition coefficients for LREE and Th extremely higher than those for heavy REE (HREE) and U; thus allanite-saturated ‘melts’ from recycled pelitic sediments would have lower LREE/HREE and higher U/Th than their sedimentary protolith. On the contrary if temperatures are high enough keep the metasomatic liquids undersaturated in such minerals, then the Th, U and REE can be released in the liquids and their trace elements contents and ratios would be dependent on other mineral phases. The high Th/U and LREE/HREE of most Italian rocks (with the exception of the Neapolitan district) suggest that the dominant metasomatic agent is a ‘melt’ generated at temperatures where rutile was stable Plotted rocks with MgO > 4.5 wt. %. Data from Conti- celli et al. (1987, 1991, 1997, 2002, 2007, 2009a, is still rutile-saturated, hence the HFSE depletion, but al- 2009b, 2010c, 2010d), Ayuso et al. (1998), Conticelli lanite and monazite were not, hence the high Th/U (1998), Pappalardo et al. (1999, 2002), D’Antonio et al. (Avanzinelli et al., 2009). In this frame the high LREE/ (1999b), Perini et al. (2000, 2003, 2004), Downes et al. (2002), Cadeaux et al. (2005), De Astis et al. (2006), HREE of most of Italian ultrapotassic and associated Peccerillo & Martinotti (2006), Di Rienzo et al. (2007), shoshonitic rocks (Figs. 8, 10, 12, 14, 16, 24, 26, and 28) D’Orazio et al. (2007, 2008), Owen (2007), Prelevic et has been ascribed to the critical role of garnet during al. (2008), Stoppa et al. (2008), Avanzinelli et al. (2008, sediment melting (Avanzinelli et al., 2008). This is con- 2010), Boari et al. (2009a,b), Cadeaux & Pinti (2009), Melluso’s unpublished data; Tommasini’s unpublished sistent with the high amount of residual garnet observed data. during experiments of melting of both basaltic (Kessel et al., 2005) and pelitic or carbonate rich (Kerrick & Con- The dominiant role of sediment derived ‘melts’ does nolly, 2005) sediments. The possibility of acquiring the not exclude the involvement of ‘fluids’ generated at low- garnet signature during by deep melting in the garnet sta- er temperature, but simply dimishes their possible effect bility filed (i.e. metasomatised mantle source deep on the final composition of the metasomatised mantle enough to stabilise garnet) was ruled out by Avanzinelli source, given their smaller ability of carrying trace ele- et al. (2009) on the basis of the lack 230Th excess (see al- ments with respect to ‘melts’ (Hermann et al., 2006). In so Asmerom, 1999). fact a widespread fluid-like component might have per- meated the mantle source of Italian magmas in a more

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 62 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ pervasive way than the melt-like metasomatism that gen- In summary Italian ultrapotassic rocks, both leucite- erates the most enriched ultrapotassic products (see later free and –bearing, with the exclusion of the Sisco one discussion section). (Corsica), were generated in a lithospheric upper mantle The role of metasomatic ‘fluids’ vs. ‘melts’ is evident enriched in K and incompatible elements by pelitic sedi- in a Ba/Th vs Th/Nb plot (Fig. 41). Negative correlation ments recycled mostly as ‘melts’ (e.g., Conticelli et al., is ubiquitous, but the various magmatic provinces define 2007, 2009a; Avanzinelli et al., 2008, 2009). different trends. The widest range is shown by the vol- Further issue to be addressed are: i) the time-related canic rock of the Roman Magmatic Province, where a de- and geographic transition from Tuscan lamproite-like ul- crese in Th/Nb, coupled with increasing Ba/Th, is evident trapotassic magmas (silica-saturated, leucite-free) to Ro- passing from the oldest and northernmost districts (i.e. man kamafugitic/leucititic-type ones (silica-understaura- Latian districts) to the youngest and southernmost one, ted, leucite-bearing); ii) the temporal and geochemical which is the Neapolitan district. Leucite-free (i.e., shosh- sequence from ultrapotassic products to shoshonites and onite) volcanic rocks from the post-caldera and the most high-K calc-alkaline rocks within each magmatic prov- recent periods of the Roccamonfina and Middle Latin ince. Valley volcanoes, the two southermost of the Latian districts of the Roman Province (above the 41st parallel; Transition from leucite-free to leucite-bearing Figs. 1 and 11), show Th/Nb vs Ba/Th values that ideally ultrapotassic rocks in the Italian peninsula fill the gap. The occurrence of significant 238U-excess in The shift from silica-saturated to silica-undersaturated volcanic rocks from the Neapolitan distric (Avanzinelli et (i.e., from leucite-free to leucite-bearing) ultrapotassic al., 2008) confirms a major role for a young (few ka, see magmas with time is not only a compositional character- Avanzinelli et al., 2008) fluid-like metasomatic compo- istic that controls the final mineralogical assemblages of nent (i.e. allanite/monazite saturated); the position of the the volcanic rocks, but it also seems to have a link with youngest products of Roccamonfina and Middle latin val- the rate of ultrapotassic magma production. Indeed in the ley in Fig. 40, along with their vicinity in space and time Western Alps, Western Tyrrhenian Sea, and Tuscan with the Neapolitan districts might indicate a role for Magmatic Provinces ultrapotassic rocks are strongly sub- such a fluid component also in these magmas. ordinate to shoshonitic mafic rocks and their derivative An increase of Ba/Th is also observed passing from magmatic terms, whereas in the Roman Magmatic Prov- ultrapotassic rocks (lamproites and minettes) to associ- ince leucite-bearing ultrapotassic magmas dominate volu- ated shoshonites and high-K calc-alkaline rocks within metrically over final shoshonites, which are confined to the products of the Tuscan Magmatic Province and West- final stage activity and do not occur in all volcanic dis- ern Alps). As discussed above, this might suggest the tricts. presence of a pervasive fluid related metasomatism Silica-saturated lamproitic ultrapotassic magmas (leu- which is overshadowed by the recycled sediment melt cite-free) are generated within a metasomatised litho- component which dominates the geochemical composi- spheric refractory upper mantle through incongruent tion of the most enriched magmas (see next section). The melting of a phlogopite-bearing harzburgitic source un- opposite occurs in the Western Tyrrhenian (i.e. Crosica der excess of H2O, then low XCO2 (Foley, 1994). Experi- province). Ultrapotassic magmas from Sisco (Corsica) mental studies have shown that silica-rich lamproitic display low Th/Nb and Ba/Th values (Fig. 41), with the magmas are generated in a lithospheric mantle source latter even lower than upper mantle values (PM = 82.2, originally depleted in the basaltic component and subse- DMM = 48-60; Wood, 1979; Sun & McDonough, 1989), quently refertilised by metasomatism in a phlogopite-or- with little HFSE/LILE fractionation and lack of Pb peak thopyroxene-olivine paragenesis (e.g., Arima & Edgar, (Fig. 10c). These characteristics suggest that the orogenic 1983a; Edgar, 1987; Foley, 1992b, 1994). Interaction component in Corsica was significantly different than with granitic melts from pelitic sediments is capable to that responsible for the other provinces, less important or stabilize modal phlogopite in a peridotitic mantle wedge possibly even absent (Avanzinelli, 2009; Conticelli et al., (Sekine & Willie, 1982a, b, 1983; Wyllie & Sekine, 2009a, 2010c). 1982). Such metasomatic enrichment through melts from recycled pelitic sediments is also able to explain the

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 63 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ higher Al2O3 content of ultrapotassic Italian magmatic 1983a; Lloyd et al., 1985; Edgar, 1987 and refences rocks with respect to within-plate ones. Conticelli et al. thereins). Thus CaO-enrichment is required beside K and (2007) have modelled for the source of Tuscan lamproite, incompatible elements, as well as a source for CO2. Such the amount of recycled crustal component needed to pro- enriching agent might be consistent with the addition of duce the observed Sr, Nd, Pb, and Os isotopic character- CaCO3 from the recycled sediments (Thomsen & istics (Fig. 40). These authors have estimated about 65 Schmidt, 2008a; Franzolin et al., 2009; Poli et al., 2009). vol. % of a crustal-derived component, introduced as Reaction of such agent with depleted peridotite generates melts within the lithospheric depleted mantle. The partial a re-fertilised phlogopite-bearing wehrlite or phlogopite- melting of pelitic sediments at relatively high-pressure, bearing lherzolite, with phlogopite and clinopyroxene within the stability field of garnet for pelitic sediments, formed at expenses of olivine and orthopyroxene within following the model of Johnson & Plank (1999) gives a the metasomatised vein network. Partial melting of such melt consistently enriched in SiO2, Al2O3, and K2O, and metasomatised veins at relatively low pressure and high depleted in MgO, and FeO, but with an mg-# within the XCO2 is able to produce strongly silica-undersaturated ul- range of 0.85 and 0.80. The composition of this mixture trapotassic magmas, from kamafugitic to leucititic in is compatible with a mineralogy dominated by phlogo- composition (e.g., Wendlandt & Eggler 1980a, b). Argu- pite/K-feldspar, with minor orthopyroxene and olivine, ments for the genesis of Italian kamafugites through the and possibly no clinopyroxene, as also shown by melting melting of a re-fertilised sub-continental lithospheric experiments on lamproitic rocks (e.g., Edgar, 1987; Fo- mantle at low pressure and under high XCO2 have been ley, 1994, and references therein). Such a high proportion shown experimentally (Conticelli et al., 1989). In addi- of metasomatic component is unrealistic to have perva- tion, evidence for the occurrence of CO2-mantle degass- sively patently modified the entire mantle wedge, but this ing beneath the Italian peninsula has been shown on the might just represents the core of a peridotite-modified basis of geophysical data by Frezzotti et al. (2009, 2010, veinlet (Foley, 1992b). Indeed “melts” flowing through this volume). the lithospheric peridotite react with the wallrock and Such a scenario also agrees with the trace element and then freezing down in a newly formed metasomatized isotopic distribution of Roman kamafugites and leuci- paragenesis, with most of the surrounding mantle unaf- tites. Indeed the shift from leucite-free to leucite-bearing fected by this reaction (Foley, 1992b; Perini et al., 2004; ultrapotassic rocks in Italy has been related with differen- Conticelli et al. 2007; Avanzinelli et al., 2009). Then up- ces in the initial composition of the recycled sediments per mantle will only be metasomatised along the main on the basis of isotope and trace element compositions of melt pathways thus generating a network of metasoma- mafic terms. Conticelli et al. (2002) suggested that the tised veins surrounded by unreacted mantle (e.g., Suen & decoupling of Sr and Nd isotopes between Tuscan and Frey, 1987; Menzies et al., 1991; Foley 1992b). Roman magmatic provinces (Figs. 36-37) was caused by Silica-undersaturated kamafugitic to leucititic ultrapo- the change of the recycled sediment from pelitic to mar- tassic magmas (leucite-bearing) are conversely generated ly. Avanzinelli et al. (2008) suggested a southward in- in a metasomatised upper mantle by partial melting of a crease of the CaCO3 sedimentary fraction related to the phlogopite-bearing wherlite controlled by a CO2 excess composition of the pelitic sediment cropping out along with respect to H2O, then high XCO2 (e.g., Lloyd et al., the Apennine chain. Avanzinelli et al. (2009) suggested 1985; Edgar, 1987 and references thereins). Considering an increasing carbonate-rich sedimentary component on 87 86 that the mantle beneath the Italian region is particularly the basis of Sr/ Sri and trace element variations ob- depleted in the basaltic component (prior to metasoma- served along the Italian peninsula. Indeed a negative cor- 87 86 tism) as evidenced by the major and trace element con- relation of Sr/ Sri vs. Sr/Ce and Sr/Rb is observed tents of most primitive ultrapotassic magmas (e.g., lamp- (Fig. 42) and it can also explain the disappearance of the roites, kamafugites and leucitites) and their olivine-spinel negative Sr anomaly passing from mafic ultrapotassic pairs compositions (Conticelli et al., 2007, and references rocks of Western Alps and Tuscan Magmatic Provinces therein), a refertilization to produce a sub-lithospheric to Roman mafic rocks (Figs. 8, 10, 12 vs. Figs 16, 18, 20, mantle source with modal clinopyroxene and phlogopite 22, 24, etc.). Sr and Ce are little fractionated when sedi- is needed (e.g., Edgar et al., 1980; Arima & Edgar, ments are recycled as ‘melts’, although they are if the

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 64 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ sediment is recycled as ‘fluid’; Sr and Rb are both easily over and along the array connecting pelitic sediments to carried by fluids, but might be slightly fractionated dur- limestone. Rocks from the Lucanian Magmatic Province ing sediment or mantle melting. Therefore the combined plot away from that array close to OIB-like compositions use of Sr/Ce and Sr/Rb ratio should provide information (Fig. 41). It is worth noting that Western Tyrrhenian (i.e. about the original composition of the sediment end-mem- Corsica) rocks lie at mid way between Western Alps and ber (i.e., carbonate- vs. clay-rich). In figure 42 the carbo- Tuscan lamproites and the field of sedimentary composi- nate-rich component, characerised by high Sr/Ce and Sr/ tions. Neapolitan district rocks and post-cladera shoshon- Rb, increases southward, with leucite-free rocks from the ites from Middle Latin valley and Roccamonfina also Tuscan Magmatic Province and Western alps plotting at plot at lower 87Sr/86Sr. This is consistent with the recent low Sr/Rb and Sr/Ce close to the composition of clay- addition of a further component, as previously discussed rich pelitic sediments. In the 87Sr/86Sr vs Sr/Ce diagram to explain the increase of Ba and U contents in the same (Fig. 42) ultrapotassic rocks, from leucite-free lamproites rocks (Fig. 41) and the 238U-excess reported for the Nea- to leucite-bearing kamafugites and plagio-leucitites, plot politan district (Avanzineli et al., 2008).

87 86 Figure 42. Sr/Ce and Rb/Sr vs. Sr/ Sri for the Italian ultrapotassic rocks.

Plotted rocks with MgO > 4.5 wt. %. Data from Conticelli et al. (1987, 1991, 1997, 2002, 2007, 2009a, 2009b, 2010c, 2010d), Ayuso et al. (1998), Conticelli (1998), Pappalardo et al. (1999, 2002), D’Antonio et al. (1999b), Perini et al. (2000, 2003, 2004), Downes et al. (2002), Cadeaux et al. (2005), De Astis et al. (2006), Peccerillo & Martinotti (2006), Di Rienzo et al. (2007), D’Orazio et al. (2007, 2008), Owen (2007), Prelevic et al. (2008), Avanzinelli et al. (2008, 2010), Boari et al. (2009a,b), Cadeaux & Pinti (2009), Melluso’s unpublished data; Tommasini’s unpublished data.

The need for carbonate-rich sediment recycled as al- km: Yaxley & Green 1994; Molina & Poli, 2000; lanite-undersaturated melts in the source of the investiga- Schmidt et al., 2004). Recent experimental studies ted magmas might provide some constraints on the con- (Thomsen & Schmidt, 2008a, b; Poli et al., 2009) have dition of sediment melting. Carbonates are expected to demonstrated that carbonate-saturated pelites (i.e. marls) behave as refractory phases at sub-arc depths (up to 180 might produce potassic granite or phonolite melts at

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 65 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ temperatures from 900 °C, at 2.4 GPa, to 1070 °C, at 5.0 From ultrapotassic to potassic and sub-alkaline GPa. As already previously shown, when these melts are volcanic rocks. mixed with depleted mantle wedge they might represent Western Mediterranean ultrapotassic rocks are inti- suitable metasomatic agents for producing phlogopite- mately associated in space and time to shoshonite and in bearing wherlite/peridotite from which kamafugitic mag- some cases to high-K calc-alkaline suites: this association ma is produced by partial melting. Allanite and monazite occurs in the Western Alps, Tuscan and Roman Provin- solubility provides similar temperature constraints: in the ces (Central Italy), but also in Murcia-Almeria (south- same pressure range (2.5-4 GPa) the temperature re- eastern Spain), Macedonia, Serbia, Montenegro, and Tur- quired to exhaust allanite are >1000 °C (Hermann, 2002; key (e.g., Conticelli et al., 2002, 2007, 2009a; Altherr et Klimm et al., 2008); admittedly this value could repre- al., 2004; Peccerillo, 2004, 2005a; Prelevic et al., 2004, sent an over-estimate, given the doped composition of the 2005; Avanzinelli et al., 2009). In the Western Alps cor- experiments and the basaltic starting sediment composi- relation with time is not clear, also because the analytical tion; experiments on clay-rich sediments showed residual error is sometimes greater than the possible time elapsed monazite up till 900°C (Skora & Blundy, 2010), whilst from one series to the other one. The best evidence of no studies are available for carbonate-rich sediment lith- this time-dependent geochemical variation can be ob- ologies. The temperature range for sediment melting served in the Tuscan and Roman magmatic provinces. In (900-1100°C) indicated by the geochemistry of the stud- most cases above a single plumbing system, stratigraphy ied rocks is much higher than that estimated at the slab/ and geochronology testify the succession from either mantle interface by thermal models of both ‘cold’ and lamproite- or kamafugite-like rocks, to shoshonites and ‘warm’ subduction (e.g., Peacock, 2003: Kelemen et al., high-K calc-alkaline rocks, through high-K shoshonites 2003). To explain this apparent inconsistency we suggest or leucitites (e.g., Perini et al., 2004; Conticelli et al., two possible scenarios; i) an increase in temperature of 2007, 2009a, 2009b, 2010d; Frezzotti et al., 2007; Boari the slab/mantle interface due to locking of the subduction et al., 2009b). The opposite is observed at Somma-Vesu- zone following continental collision; ii) the physical in- vius volcano where plagio-leucititites follow shoshonitic corporation of portions of the subducted sediments from volcanic rocks (Cioni et al., 2008, and references there- the top slab into the mantle, either by imbrication or via in), similarly to the succession observed at Stromboli vol- diapirs (e.g., Kelemen et al., 2003; Klimm et al., 2008), cano in the Aeolian Arc (e.g., Ellam et al., 1988; Pecce- and their melting in the hot central region of the mantle rillo, 2001, 2005a; Alagna & Peccerillo, 2010, this vol- wedge. ume). It is worth to note, however, that a recent study by The geochemical transition between magmatic series Tommasini et al. (2011) indicates a more complex mech- differently enriched in K and incompatible trace elements anism for the metasomatic enrichment of the mantle- (i.e. from ultrapotassic to shoshonites or vice versa) has source of Mediterranean lamproitic magmas. These au- received at least three explanations: i) relaxation of iso- thors have found that a multiple metasomatism event is therm that intercepts the solidus of variably metasomat- needed to constrain the extreme enrichment in K and ized upper mantle levels, with the most strongly meta- concomitant fractionation of Th and Sm with respect to somatized mantle at deepest level (Peccerillo, 2005a; La. This emerges from a widespread positive Th/La vs Frezzotti et al., 2007); ii) either increase or decrease with Sm/La correlation found in Tethyan Realm lamproites time of shallow level carbonate assimilation, the former (including those from TMP, Corsica and Western Alps claimed to explain the Somma-Vesuvius case (Iacono- discussed in this study) and associated shoshonitic rocks Marziano et al., 2007, 2008); iii) incremental partial (Tommasini et al., 2010; Conticelli et al., 2010b), which melting of a manle source metasomatized in a veined net- is opposite to what observed in subduction related mag- work and dilution of the vein end-member by interaction mas worldwide (Plank, 2005). with surrounding peridotitic country-rocks (e.g., Foley, 1992b; Conticelli et al., 2002, 2007, 2009a; Perini et al., 2004; Avanzinelli et al., 2009; Boari et al., 2009b).

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The first hypothesis fails to explain why earlier mag- wallrock, freezing down as a newly formed metasomat- mas, formed at deeper levels, did not interact with upper- ized paragenesis, leaving most of the surrounding mantle most metasomatised levels. In addition, all primitive maf- unaffected by this reaction (Foley, 1992b; Perini et al., ic magmas independently from their K2O contents seem 2004). The vein hypothesis is also consistent with most to have been in equilibrium with a mantle source charac- of the metasomatized peridotites observed in nature (e.g., terized by the same depletion prior to metasomatism Rivalenti et al., 1995, 2007; Zanetti et al., 1999; Ram- (Conticelli et al., 2007). In fact, differences in the mantle pone et al., 2010). In the veined model, the mantle source source residuality are not observed within the same reacts differently during upward migration of the iso- plumbing system, but rather between Latian and Neapoli- therms. Initially, partial melting will affect the portion of tan districts. Therefore the sources of ultrapotassic and the mantle with the lowest liquidus temperature, which is shoshonitic magmas should not be too distant from each the inner portion of the veins characterized by pure meta- other. somatic mineralogy (Foley, 1992b, 1994). The tempera- Recently Iacono Marziano et al. (2007, 2008) have ture increase, due to post-orogenic isotthrerm re-equili- called for strong involvement of sedimentary carbonate brium, triggers partial melting also of the surrounding assimilation in the Italian rocks to justify the derivation mantle alolowing the interaction between vein and coun- of ultrapotassic leucite-bearing rocks from shoshonite. try rock, thus diluting the metasomatised component Such a possibility was firstly postulated by several au- (Conticelli et al., 2007). Incompatible trace element and thors in the early twentieth century (e.g., Daly, 1910; isotopic variations observed for the Western Alps, Tus- Rittmann, 1933) and later discounted by Savelli (1967). can and Roman Magmatic Province, with the exception Iacono Marziano et al. (2007, 2008), on the basis of ex- of the Neapolitan district, which requires an additional U- perimental data, justify the passage from shoshonite to ei- rich ‘fluid’ component (Avanzinelli et al., 2008), can be ther leucititic or plagioclase leucititic magmas through explained in terms of mixing between a strongly alkaline limestone assimilation plus clinopyroxene crystallisation. component, either lamproite for Western Alps and Tusca- Conticelli et al. (2009b) tackled this issue focusing on ny leucite-free rocks or kamafugite for Roman leucite- leucite-free shoshonites and leucite–bearing plagio-leuci- bearing ones, and a probably sub-alkaline end member tites from Roccamonfina volcano. The authors attempted (i.e., high-K calc-alkaline). Indeed, it has been argued modelling of AFC processes able to drive the composi- that the surrounding lithospheric mantle bear itself a sub- tion of magmas at Roccamonfina volcano from the post- alkaline composition, possibly due to a pervasive ‘fluid’- cadera shoshonites to the pre-caldera leucitites and pla- like metasomatism, similar to that of many arc magmas gioleucitites and vice versa: they demonstrated that AFC worldwide, as opposed to the localised ‘melt’ metasoma- processes, although important for the chemical evolution tism that give raise to the vein network (Conticelli et al., within each magmatic series, could not be responsible for 2009b; Conticelli et al., 2010b). Passing from lamproites the trasition from ultrapotassic leucite-bearing magmas to to shoshonites and high-K calc-alkaline rocks, the influ- leucite-free shoshonites or vice versa. In the specific case ence of the vein budget (i.e. high Th/Nb, low Ba/Th) over of Somma-Vesuvius further evidence against a major role the composition of the erupted magmas becomes less im- for crustal contamination are reported by Del Moro et al. portant in favour of that of the surrounding mantle (Fig. (2001). 41). The increase of Ba/Th toward the less enciched As previously discussed extremely high contribution terms (i.e. shoshonite and high-k calc-alkaine) suggests from recycled crustal material are required in order to indeed that the surrounding mantle has been itself affec- generate the most extreme composition of Italian lamp- ted by a ‘fluid’-like component enriched in Ba with re- roites and kamafugites. It is unlikely for such a high pro- spect to Th. This pervasive metasomatism can also facili- portion of metasomatic component to pervasively modify tate melting of the lithospheric mantle surrounding the the entire mantle wedge, whilst it have been proposed vein that was deemed as highly depleted by previous ba- that it might affect only localised portions of the mantle saltic extraction on the base of major elements and oli- in a network of metasomatic veins (Foley, 1992b). In- vine-spinel pairs and that would result otherwise refracto- deed “melts” flowing through finite path trhough the ry. lithospheric peridotite, react with the surrounding

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The process of diluting the vein contribution by in- ultrapotassic and associated rocks (see references in Pec- volving increasing proportion of the surrounding litho- cerillo, 2005a and Conticelli et al., 2009a). A within- spheric mantle during partial melting produces isotopic plate mantle component has been proposed to be in- mixing trends, which are not distinguishable from simple volved, albeit in different style and extent, in the genesis mixing between two end-member magmas. However, of the southernmost Roman magmas, namely those of the simple magma mixing at shallow level, within the upper Neapolitan district (Ellam & Hawkesworth, 1998; Becca- crusts has to be ruled out on petrographic grond, since luva et al., 1991; Ayuso et al., 1998; Peccerillo, 2001; most of the high-MgO rocks can be confidently consid- Gasperini et al., 2002; De Astis et al., 2006; Bianchini et ered to be very close to primary magmas compositions. al., 2008), and at a still minor extent in the final activity Most of the rocks under consideration have olivine on the of the southernmost Latian districts (Conticelli et al., liquidus, with compositions in equilibrium with the bulk 2009b). rock. The latter is considered to be the composition of the In the case of Roccamonfina volcano an abrut shift magma from which olivine crystallises. If magma mixing from pre- to post-caldera volcanic rocks is observed, with occurred at shallow levels, olivine would have begun to decrease of alkaline degree and total abundance of in- crystallise and mixing would have altered the composi- compatible elements with time. All these characteristics tion of the magma driving it away from equilibrium with might be consistent with the process of increasing inter- olivine. action proportion of melts from surrounding mantle with A further possibility is represented by the recent arriv- respect to vein melts. In this case, however, the vein vs. al of a fluid-like metasomatic agent that overprinted the wall-rock mantle interaction does not explain the large old metasomatic signature and trigger partial melting also variation in Sr-Nd-Pb isotopes observed (Figs. 36, 37, in the surrounding mantle. This is likely to be the case and 38). Indeed, the expected isotopic composition of the under the Neapolitan District, where such arrival is testi- surrounding mantle, which is low Sr and high Nd isotope fied by the 238U-excesses (Avanzinelli et al., 2008). In ratios, respectively, would suite the versus of variation in general this process should imprint a different geochemi- the shoshonites; however, a depleted mantle is expected cal and isotopic signature in the most recent sub-alkaline to have developed low U/Pb and Th/Pb and thus to have magmas (e.g., De Astis et al., 2006; Boari et al., 2009b; an unradiogenic signature, rather than the radiogenic one Conticelli et al., 2009b). necessary to explain the increase in Pb isotopic ratios towards the shoshonites (Fig. 38). Early Roccamonfina ul- Within-plate component trapotassic volcanic rocks (leucite-bearing) display Sr- The presence of this component and its origin is po- Nd-Pb isotopes well within the range of values of the tentially the essence of the debate about plume vs. sub- other Latian districts, whereas the rocks from the final duction-related origin of circum-Tyrrhenian magmatism. stage of activity display values well within the field of Namely, primordial mantle normalised incompatible the Neapolitan district and pointing to the isotopic com- trace elements patterns of the potassic rocks from the Lu- positions of the Lucanian Magmatic Province (Figs. 36, canian Magmatic Province are clearly different from 37, and 38). The volcanoes of the Neapolitan district those of the other provinces (Fig. 34c). Troughs at Ta, show a more abundant within-plate component with re- Nb, and Hf as well as LIL vs. HFS elements fractiona- spect to Roccamonfina final activity both in terms of iso- tions are strongly reduced, especially in the most recent topic (Figs. 36, 37, and 38) and incompatible trace ele- products of the Monticchio lakes. Isotopic signature re- ment compositions (Figs. 30, 31, and 32). To explain this sembles that of within-plate magmas (Figs. 35, 36, and within-plate component in the ultrapotassic and shosho- 37) with values close to those of the OIB enriched terms, nitic rocks of the Neapolitan district, Beccaluva et al. although a lithospheric orogenic signature appers to be (1991) suggested the occurrence of a mantle wedge char- still present in some way (e.g., Downes et al., 2002; De acterized by an OIB signature prior to metasomatism Astis et al., 2006; D’Orazio et al., 2007, 2008). Indeed, south of the 41st parallel. This possibility however, does Lucanian Province volcanic rocks also display the most not explain i) the occurrence of this component limited to radiogenic Pb and Nd and the least radiogenic Sr isotopic the final stage activity of Roccamonfina, a volcano compositions with respect to all Western Mediterranean slightly north of the 41st parallel; ii) the observed

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 68 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ geochemical trends from Roccamonfina to Lucanian During Tortonian, shoshonitic and high-K calc-alka- rocks passing from Neapolitan ones; iii) the absence of line rocks were emplaced along the western margin of the the within plate component in the early Roccamonfina Tyrrhenian Sea (Fig. 43) possibly related to a westward rocks; indeed if mantle wedge had an OIB signature prior dipping Apennine subduction (e.g., Faccenna et al., to the metasomatism, it is conceivable that this signature 1997; Jolivet et al., 1998; Rosembaum et al., 2002, 2004, would be at some extent preserved also within the veins 2008; Rosembaum & Lister, 2004). Backward migration producing early ultrapotassic rocks. of the subducted slab and consequent isotherm relaxation triggered the generation of lamproitic magmatism in the Geodynamic implications Italian peninsula after the beginning of continental colli- Ultrapotassic and associated shoshonitic to high-K sion. Shoshonites and high-K calc-alkaline rocks fol- calc-alkaline volcanic rocks of the Italian region have lowed the eruption of lamproites (Fig. 43) as a conse- been produced from anomalously enriched upper mantle quence of the increasing heat flow that brought to melt source following sediment recycling at a denstructive larger portion of the mantle wedge, with surrounding plate boundary. Sediment-derived ‘melts’ represent the mantle becoming dominant with respect to metasoma- dominant metasomatic agent responsible for the estab- tised veins. Magmatism progressively moved eastward. lishment of a metasomatic vein network, but a more per- The metasomatic event was possibly not generated vasive ‘fluid’-like metasomatism is also present. The ex- during the Apennine subduction but through several treme enrichment in Th and the fractionated REE pattern events of subduction of the Tethys Ocean beneath the Eu- of the erupted rocks suggests the presence of garnet in ropean plate (i.e., Tommasini et al., 2010). During the the residuum during the partial melting of the recycled upper Pliocene to lower Pleistocene the lamprotitic to sediments brought into the mantle through subductionand shoshonitic magmatism furtherly migrated eastward with crustal delamination. This implies that temperatures dur- an arcuate distribution immediately back to the Apennine ing sediment partial melting were high enough to exhaust chain where post-orogenic extension started to produce other accessory phases, such as allanite and/or monazite. NW-SE elongate basins (Fig. 43b). These temperatures are higher than those generally ex- After a hiatus of several hundred thousand years, dur- pected at the slab/mantle interface, indicating that sedi- ing the Middle Pleistocene (Fig. 43c), magmatism shifted ment melting occurred in the hot, central regions of the its composition from silica saturated and leucite-free to mantle wedge rather than at the slab/mantle interface. silica-undersaturated, with formation of kamafugitic to Large HFSE negative anomalies and fractionated REE plagioclase leucititic and leucititic magmas, which were patterns require rutile and garnet in the residuum. erupted along the same plumbing system used by the late The first episode of magmatism occurred during the Tuscan magmas. In some cases hybridism between Ro- Oligocene within the Western Alps, and it was related to man and Tuscan magmas took place during the early pha- the Alpine collision. Lamproite-like ultrapotassic mag- ses of the Roman volcanism (e.g., Palaeo-Bolsena, Rio mas were generated in strict association with shoshonitic, Ferriera formation at Vico, Morlupo volcanic rocks at Sa- high-K calc-alkalic and possibly calc-alkalic magmas. batian district), in other cases reactivated old Tuscan Magmas were emplaced during the post-collisional crystallising magmatic reservoirs bringing hybrid rocks stages of the Alpine chain. Peccerillo & Martinotti to form the Amiata volcano. (2006), provides evidence that the same metasomatic Al- The newly arrived magma was silica undersaturated pine event occurred also in Corsica, and Tuscany, well and was generated in response of the recycling of carbo- before than Apennine orogenic movements started. Reac- nate-rich pelitic sediments within the mantle wedge dur- tivation of this old metasomatised should has promoted ing last collisional phases. This carbonate-rich metaso- the partial melting and the formation of Corsica and Tus- matism produced phlogopite-bearing wehrlitic veins, can lamproites. Unfortunately, the Sisco lamproite (Cor- which partial melting under high XCO2 generated kama- sica) has a within plate signature that dominate over the fugites and leucitites. A further eastward migration of orogenic ones, whereas the Tuscan lamproitic rocks have magmatism occurred at the passage from Middle to Up- a slightly different isotopic signature with respect to the per Pleistocene with the formation of kamafugitic mag- Western Alps (Conticelli et al., 2009a). matism in intra-apennine area (Fig. 43c).

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Figure 43. Schematic tectonic evolution of the circum-Tyrrhenian area since late Miocene.

CMP = Corsica Magmatic Province; TMP = Tuscan Magmatic Province; RMP-LD = Roman Magmatic Province – Latian Districts; RMP-ND = Roman Magmatic Province, Neapolitan District; LuMP = Lucanian Magmatic Province; AA = Aeolian Arc Magmatic Province. Redrawn after Faccenna et al. (2004), Cifelli et al. (2007), and Avanzinelli et al. (2009).

During the late Pleistocene asthenospheric mantle trhough.located close to the bradanic through. Trace ele- from the foreland start to inflow within the mantle wedge ment ratios and isotopic values are consistent with the in- through a slab-tear located close to the Bradanic volvement of a within-plate mantle component similar to

Leucite-bearing (kamafugitic/leucititic) and –free (lamproitic) ultrapotassic rocks and associated shoshonites from Italy: constraints Page 70 on petrogenesis and geodynamics Journal of the Virtual Explorer, 2010 Volume 36 Paper 20 http://virtualexplorer.com.au/ that of the asthenospheric mantle of the foreland, the at Vulture volcano marks the vertical rupture of the sub- Adria microplate. The Lucanian Magmatic Province with ducted plate. In Lucanian Magmatic Province this scenar- the nested Vulture and Monticchio volcanoes is located io is also supported by a 230Th-excess measured in a at the very extreme edge of the overriding plate (Fig. 11), sample from the Monticchio Lake maars, suggesting an where the mantle wedge is reduced or absent. Toroidal important role for adiabatic melting in an up-welling as- inflow of hot asthenospheric material into the mantle thenospheric mantle source (Avanzinelli et al., 2008, wedge will produce partial melting of the convecting 2010). mantle, which interacts with the small amount of metaso- On the basis of the time of occurrence of the within- matised mantle wedge peridotite as recorded by Downes plate component we might suggest that the slab-tear in et al. (2002). This would results in magmatic rocks with correspondance of the Vulture volcano formed before the intermediate geochemical characteristics between oro- middle Pleistocene, indeed the early Vulture volcanic genic and within-plate. Inflow is favoured by the south- products, which are as old as 0.7 Ma, show the presence eastward roll back and progressive fragmentation (i.e., of the within-plate component. However, the slab-tear detachment: Wortel & Spakman, 2000) of the subducting opening northward occurred significantly later. Indeed plate which is now reduced and segmented into narrow the ultrapotassic magmatism during the Middle Pleisto- tongues from one original slab (Faccenna et al., 2004; cene at Roccamonfina and Middle Latin Valley volca- Rosembaum & Lister, 2004; Mattei et al., 2007; Rose- noes was not affectetd by this component. The within mbaum et al., 2008). The asthenosperic mantle flow plate component appears in these volcanoes at about 035 through the tear within the subducted slab in correspond- Ma. Since then the within-plate component invaded the ence of the Vulture volcano (Wortel & Spakman, 2000), Neapolitan mantle wedge. with time moved into the southern Italian mantle wedge. Eventually, during the Holocene a further metasomat- The motion of the asthenospheric mantle from the fore- ic agent arrived in the Neapolitan region to account the land within the mantle wedge is recorded by the less evi- U-Th isotopic characteristics of Vesuvius, Ischia and dent within-plate signature observed from volcanoes of Campi Flegrei magmas (Avanzinelli et al., 2008). Indeed the Neapolitan district (e.g., Peccerillo, 2001; De Astis et the U-Th disequilibria require the addition, shortly before al., 2006), and at a less extent by the sub-alkaline recent the eruption of the magmas of the Neapolitan district volcanic rocks of the Roccamonfina, and even lesser ex- (<10ka), of a U-rich component, which has affected nei- tent of the Middle Latin Valley (Boari et al., 2009b; Con- ther the Latian district of the Roman Magmatic Province ticelli et al., 2009b). nor the Monticchio lakes volcanic products of the Luca- The location of the main tears are controlled by the nian Magmatic Province (Avanzinelli et al., 2008). presence of lateral heterogeneities in the subducting slab such as those represented by the transition from the Ion- Acknowledgements ian oceanic lithosphere to the Apulia and Hyblean conti- The authors wish to thank D. Prelevic, S. Foley, Rob nental lithosphere. Such heterogeneities are responsible Ellam, K. Bell, F. Sani, G. Bianchini, C. Faccenna, V. for the curvature of the Calabrian Arc and for the major Morra, and L. Morbidelli for stirring and focussing dis- fragmentation of the subducting plate. In the Vulture vol- cussion and in some cases for suggestions at different cano area, the presence of a lateral tear in the subducting stages of the manuscript preparation, L. Fedele for sup- slab is suggested by the differing behaviours of the fore- plying the electronic base of figure 29. Financial support land areas southeast and northwest of the volcano. These was provided by the Università degli Studi di Firenze areas correspond to the transition from the thick carbo- (DST – ex 60% funds) issued to Sandro Conticelli, by the nate Mesozoic succession of the Apulian platform, which Italian Ministry of Education and Research (MIUR) itself corresponds to the buoyant outcropping Apulia through PRIN_2008 (research grants #: foreland, to the transitional and basinal facies outcrop- 2008HMHYFP_002; 2008HMHYFP_003; ping in the Gargano area. The beginning of magmatism 2008HMHYFP_005).

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